Building a new room onto an existing structure

[LynnAxel]

I own Home Designer Architect. But am trying out the Home Designer Pro. Even using the pro version i cannot figure out how to add a new room onto an existing structure.

The roof lines need to stay as they are for the existing home when adding the new roof over the new room. When i add the additional square footage to allot for the new room the roof line changes; the program acts as if this is an entire new structure when what is needed is the new roof to tie into the existing.

if new room additions are an option with the software please help

thank you