Using your own cuttings to produce new plants can be quite satisfying. It's like what Nature does except on a much smaller scale. However, not all cuttings morph into new plants without help, and here is where rooting hormones
https://www.gardenmyths.com/rooting-hormones-what-are-they/

 come in. The naturally occurring part of a plant that controls development is called auxin, and you can buy rooting hormones that contain this element, to help your cutting find its potential as a growing plant.

Many people will tell you that you can use things found around the home as rooting hormones. 
https://preparednessmama.com/natural-rooting-hormone/

This is true, although the success rate isn't as high as with commercial rooting hormones (and, to be fair, still involve purchasing something). If you're going to spend money on helping your cuttings flourish, then you might as well spend that money in a high-impact way. The products I've identified below are the best rooting hormones out there, and they are designed to help your cuttings grow by simulating the natural process and then stimulating that growth.

Keeping reading for more.

KEY TAKEAWAYS

To compile this list, I've examined dozens of products, consulting customer and expert reviews. I've also relied on my own expertise as a gardener. I've had my fair share of success in regrowing from cuttings, and you can, too. I'm also here to tell you, however, that the success rate is not 100 percent. Just keep that in mind. By starting with a cutting, you're not starting with a fully plugged-in entity, anyway. But by using one of the products I've laid out for you, you can get a great charge out of seeing your own growth in just a few weeks.

Overall, the best rooting hormone is HydroDynamics Clonex Rooting Gel. You get the best of everything with this one. 

Why this is a quality choice: It's a gel, so the treatment stays in contact with the cutting long after application. In fact, the gel seals the cut tissue so the cutting can grow whole. Clonex has made this product since 1988, and it's consistently been a top seller, for very good reason. You can even use it on fruit trees.
https://www.amazon.com/dp/B004Q3NN4W

Who is this for: Beginners and seasoned gardeners alike will benefit from this rooting hormone gel. You wouldn't expect a perfect success rate because that's the nature of such an undertaking, but many users have reported very high numbers of cuttings that have thrived and grown.

Flaws but not deal-breakers: You'll need to  keep the gel refrigerated in between uses, to maintain freshness and to prevent hardening.

A close second is Garden Safe Take Root powdered rooting hormone. As a powder, it's longer lasting than gel products. 

https://www.amazon.com/dp/B09WZHXNQ2

Why this is a quality choice: The active ingredient, IBA, is so very similar to your plant's naturally occurring hormones. The powder is very easy to use and doesn't require multiple doses.

Who is this for: Users have found success in growing roses, African violets, poinsettias, and even woody ornamentals from cuttings, using this powder.

Flaws but not deal-breakers: Some users have found the containers to be smaller than they anticipated. But remember: A little powder goes a very long way.

Best Budget
Garden Rich Root&Grow
https://www.amazon.com/Bonide-Root-Grow-Concentrate-16/dp/B001O87BKY/
You'll well appreciate what this little liquid can do for your houseplants, vegetables, fruit trees, trees, and shrubs. It puts its active ingredient, IBA, to work right away,  stimulating root growth. It's a 4–10–3 fertilizer (4% nitrogen, 10% phosphate, and 3% potash). It's meant as a concentrate, so mix it with water and pour it directly on the soil and roots. 

Best for Water Propagation
Hormex Vitamin B1 and Hormone Concentrate
https://www.amazon.com/Hormex-HC1208-Conc-Vitamin-Concentrate/dp/B01FRUT9FY

I prefer to mix liquid with liquid. Mixing in a powder into your propagation water might just dissolve it too quickly. Using a liquid like this Hormex product is the way to go. It is a concentrate, so you will have mostly water, anyway. 

Why this is a quality choice: The active ingredient, NAA, is a hormone in the auxin family. The addition of Vitamin B1 helps promote growth of stem and foliage.

Who is this for: This fix isn't quick and dirty, but it is relatively straightforward. If you're looking to propagate your cuttings in water, then this is the best choice for that purpose. It works on indoor and outdoor plants.

Flaws but not deal-breakers: It is very concentrated. It is tempting to use too much. Carefully read the label.

Best Organic: Katyayani Root Fast
https://www.amazon.com/Katyayani-Root-Fast-Rooting-Hormone/dp/B0BP2QD6WV

This company is all about organic, and their Root Fast product is the specialty product you need to flowers, woody ornamentals, and other cuttings. 

Why this is a quality choice: They specialize in sustainable development. It's easy to use and, unlike other products, can be used year-round.

Who is this for: Anyone who wants to go and grow and stay organic will appreciate the approach.

Flaws but not deal-breakers: It is a powder, which might not be suited for all cuttings.

Best for Roses: RootBoost Rooting Hormone
https://www.amazon.com/Gardentech-RootBoost-Rooting-Hormone-Feeder/dp/B0068IS16S

Many people really like roses, and it can be very satisfying to grow a new rose or even a whole new bush from cuttings.
https://www.countryliving.com/gardening/a32083091/how-to-grow-roses-from-cuttings/

If you want to give your cuttings a great chance at success, then you'll want to use rooting hormones, and one of the best out there for roses is RootBoost Rooting Hormone. One of the active ingredients is Hormodin 1, a form of IBA proven to accelerate root growth. This is a powder, so don't mix it with water, as you would a liquid rooting hormone, because water will actually dilute the powder and, in the process, the IBA.

Why this is a quality choice: Professionals use IBA to stimulate their cuttings growth, and you can too. Roses take a bit of time to regrow, but they will. After a few weeks, you should see what you're after.

Who is this for: If you're serious about roses, then you want to give your plantings the best choice for success. Why spend all of that money on rose shield and all of that time pruning if you're not going to make the same commitment to growing new?

Flaws but not deal-breakers: It's a tiny bottle, but you don't need much. The manufacturer says it's enough for hundreds of plantings.

BUYING CONSIDERATIONS

Consistency of product
In most cases, you will be choosing between powder and gel. Each has its pluses and minuses. The application of a powder rooting hormone does take a little more effort and equipment, since you will want to put a bit of powder on a bit of cardboard or a paper plate or some temporary surface and then roll the cutting in the powder, rather than dipping the cutting into the powder container. With a gel, you will also want to spread a bit in a bowl, rather than dipping right in the bottle.

Scope of need
Unless you're a commercial grower or someone who just loves growing their own roses, you likely won't need a huge amount of rooting hormone. Experiment a bit by buying a small container and go from there. Especially with concentrates, a little truly does go a long way.

Planning ahead
By using rooting hormones, you are significantly increasing your chances of seeing healthy growth for your cuttings. It's important to think through the possible extra garden space that you may need when this happens. It will take a few weeks for the rooting hormones to take effect, but they will and so you should be ready for these additions to your plantings.

How I choose these products

I undertake careful analysis, reading reviews and papers dealing with the subject matter. I sift through the various product listings, scrutinizing the active ingredients and comparing one product to the next, searching for the best outcome. I find out as much as I possibly can and consult many sources before making these recommendations. I also speak from my own experience as a grower. There's nothing more frustrating than failing to get something to grow. I understand that. The purpose of this analysis is to help you avoid such frustrations, by making intelligent choices for aiding your cuttings to grow and mature in the way that you want them to. And I wouldn't recommend to you anything that I wouldn't use on my own cuttings, in my own garden.

Final Verdict
After all of that, my top pick of the best rooting hormones is Clonex Rooting Gel, from HydroDynamics. It's easy to use, it does what's advertised, and the company has a great many satisfied customers who agree.

FAQs

Can you use too much rooting hormone?
Yes, you can. These products have recommended dosages for a reason. The makers have tested their products incessantly in order to find the correct amount to use with each application. Although dosing with rooting hormone is a onetime deal (since you likely won't be digging up those plantings just to reapply), you can still do exactly that type of damage that you're trying to avoid by using too much. You can get too much of a good thing, and this is one way to do it. Stick with what's on the label.

What is rooting hormone made of?
This varies, slightly. Most rooting hormones simulate the use of auxins, which help a plant grow. Common active ingredients found in rooting hormones include IBA (indole butyric acid) and NAA (naphthalene acetic acid), both of which are specially prepared approximations of the plants' naturally occuring IAA (indole acetic acid).

What are the examples of rooting hormone?
Rooting hormones come in three types: gel, liquid, and powder. Each type has its own benefits and drawbacks, depending on the needs of your cuttings. Both liquid and powder rooting hormones will likely be mixed with a bit of water, whereas gel will be used on its own.