Hold on, let's back up... you say you have two rose bushes. That means the problem is very easy to manage without using poisons. All you need to do is get a hand-held spray bottle, fill it with water, add some liquid soap, shake it up, and spray it on the aphids. The soap will suffocate them and they will die off right away. Rinsing the plant with a hose spray can also work to get rid of them. Once the aphids are dead or gone, they will no longer produce the "honeydew" that the ants like. This means the ants, in turn, will go away (you don't need to kill them, too - they are no threat to your roses).