Since I'm installing a DASC on my Z3 (M44), I bought
this book. One of the installation example it gives is a twin-screw (not Roots) installation on an BMW M44. It also gives you an idea of what to consider when doing a custom installation (blower displacement, pulley size, boost, intercooler size, etc).
I would recommend it big times, particularly if you're thinking about a custom setup: regardless your knowledge and experience with SCs, I think having a structured and organized way to think the project through can only benefit the outcome.