I have an old house with unique, but simple profile, molding and
quarter circle pieces at the corners.

I'm wondering if anyone knows if it's possible to get a large bit made
that I can mount on my router table that I could use to make more of
the straight molding? I'd also like to to find a source to make a
rosette cutter for quarter circle pieces.

there is a company locally that charges a 200.00 setup fee to make the
straight molding, plus an extra charge per foot, and they won't hold
the blades for your pattern, so if you decide you need more at a later
date, you're out for another 200.00.

advice?