Roller cam and turbo charging

Reading through the "turbo bible", it says flat tappet is better for lower boost levels.
I'm planning 6-15 psi with my build. My machinist is pretty convinced I should go roller, I'm not against it, but it is contrary to what I've read. What's the consensus? He says "I put a roller in everything I can". Lol
This will be a street driven set up, with the occasional track day.