You planned incorporate roundcube to replace a mail manager on coreBOS?
Legally we cannot do that. The licenses of both applications are incompatible, they cannot be mixed. I know Yetiforce is doing that, but they can't (unless they have some special permission)
We have a standalone integration like gmail:
http://corebosmail.tsolucio.com/
Not only Yetiforce
Exist vTiger Add ons too