A roots blower adds more stress to a motor than a centrifugal blower. On a NA engine, peak cylinder pressure is reached on a motor at its peak torque, and since the roots makes power down low, it increases the cylinder pressures even more at peak torque. This will cause more stress on a motor. A centrifugal blower will make power up top, when cylinder pressures drop.
Roots blowers, more power down low, but put more stress on the engine. Centrifugal blowers, put less stress on the engine, but max power is gained up top.
If your debating between the Paxton kit and Roe's, get the Roe. It is complete, simple, and very well priced for a complete kit. You buy the kit, and your finish. This is what I plan to buy. I have built many cars, and for mine, I want a complete solution without having to monkey around with extra parts. It is the easiest and most reliable way from a DIY perspective.
The Paxton kit does not have a well laid out fuel and tuning solution, so you will be adding more parts to it until your car is a science project. If you know your stuff, then this can be a fun and powerful route, but more costly than Roe's. If you can spend the money, get a centrifugal supercharger kit from a tuner, who can give you a complete solution.