I am 8 months down the road after the robotic. I have a bad margin like you. This is a very hard personal decision to make. You should do just as your Doctor says and I even recomend meeting with a regular oncologist. My Doc said they now recomed seeing a Oncologist and radiation oncologist as a matter of protocol when there is a bad margin. Many here in our situation have decided to radiate adjuvantively while others watch their PSA's very closely and consider salvage radiation if their PSA goes up measurably. I am the latter.
My Urologist who is also an oncologist, recomended if he was in my shoes he would watch and wait based on what he saw. My margin was a single margin and very short. Radiation Oncologist stated that maybe at most two cells could be left behind. There is the rub, two cells can cause alot of problems or die off. No one knows.
I think about my decision alot, alot. My PSA's were undetectable at 6 weeks, 3 months and 6 months this I was told is a positive thing.
If you choose adjuvant ratiation, which I dont blame you one bit indeed, they would not be able to start radiation until you heal adequately which can differ from man to man. But for sure no sooner than 3 months. You should be able to see at least your 6 week PSA and your 3 month.
I believe that adjuvant radiation is administered in lower doses than salvage radiation.
I wish you all the best in making your decision. Knowledge is power. Do what's right for you. Do some research on positive margins. A good sight is UroToday.com. Its free