I know, it really is sad. Roman is one of my favorites, but he needs to take some time to be with his family and focus on getting better. He will be back, he kicked leukemia several times before, he can do it again. He's a fighter (no pun intended).
Depending on the type of leukemia he will likely be away for years. Realistically speaking maybe a he could do few part time cameos in the next 2 years, nothing more.