In planning my new house build, I would like to get the roof and soffit penetrations done immediately after framing and before plumbing rough-in.  We're doing a sealed attic with closed-cell foam against the underside of the roof deck, so I'll need to have the plumbing stack vent in place.

Is it feasible to put in the stack vent and then figure out how to connect all the internal stacks to it later?  Is a single vent OK or does this depend on number of fixtures?  Any other suggestions?

Thanks.

The way I have handled this is to spray the underside of the roof and then call in the plumber.  After the plumber has done all the damage he can do, then touch up the spray foam.

I would discuss this with a plumber but, if you're using ABS, there shouldn't be an issue with running a stack vent out and temporarily sealing it to the roof jack, say with duct tape.  Then when the time comes to make your tree you could take off the tape and slide the ABS up and start connecting your tree.  Whether or no you need more than one stack will depend on the number of fixture units and the location of them.