Did you mean to post this in the ++ forum, or the Rosetta 3 forum? I’m assuming the latter. If the former, ++ is no longer under development; you’ll probably have to try iterating between the two modes (and will have trouble getting help).
Rosetta3 in general can address the problem of two proteins and one ligand, but I don’t know that there is a prewritten tool for it. You may need to generate your own using RosettaScripts. I’ve forwarded the question to the docking and ligand guys for comment.