By doing Kybella on my banana rolls, will other areas like saddle bags increase in size?

Kybella is only approved for treating submental fat under the chin. While it is used off-label by some physicians, the safety of using Kybella in larger areas like you are describing has not been well-documented at this time. I would likely recommend liposuction or CoolSculpting for these areas, as they are minimally-invasive surgical procedures that will remove the fat and give you the results you want in a single treatment session. 
As long as you keep your weight relatively the same, within five pounds, both liposuction and CoolSculpting offer very long-term results. If you gain 15 or 20 pounds, it is not fair to blame the procedure for fat in new areas. Instead, it is old fashioned diet and exercise that need to be factored in. As you age, it is harder to lose weight and hormones play a factor as well. Realizing this, one must eat less or exercise more through the years to avoid weight gain. Try to weigh yourself on every birthday and record it. This weight should be your goal and your guide for a healthy weight and fit toned body through the years. An experienced, board-certified dermatologist can assess you in person and determine whether you need to treat both areas or if you will get the results you want from addressing the saddlebags alone. They can also help you reshape the body at a weight that is comfortable for you to maintain. Then you will have the figure you want for many years.

Kybella is an injectable fat reducing treatment that is only approved to treat submental fat under the chin. It is not designed for use in larger areas like you are describing. I recommend you schedule a consultation with a board-certified dermatologist for a full assessment and discussion of your concerns and goals. It is likely a liposuction procedure will meet your needs best. In my office, we use the Awake liposuction technique, which can be performed using local anesthetic and typically requires less downtime than traditional liposuction techniques. Treating your backside will not increase the size of your saddlebags. However, reducing the size of the buttocks may create the illusion the saddlebags are larger due to changes in proportion. An experienced doctor will be able to recommend the right treatment plan for you based on your specific needs and aesthetic goals. 

hello, quick question. Kybella is targeted fat reduction. The other areas that are not injected will not get larger unless you gain weight.