Roots is not going to work as it will require you modify the intake plenum which is ABS plastic. Very difficult to do. Your bet is to get ASA, Mosselman or Rotrex kits. Check out AAtuning, they used to do wicked rotrex for the M3.
(Some

aussie engineered a once-off roots with a custom intake plenum integrated. Must be a real labour of love to design such a complex piece).
Mounting bracket mounts with a strange curve on the front of the block with fan belt off and possibly alternator maybe loosened to fit it. Very tight there!. It has a tensioner integrated and needs a special longer single belt to drive everything else including the blower.
Justin from RedFive motorsport used to built a serious ProCharger blower in the M30 block of the 535i back in 01. That had a solidly engineered bracket to hold the huge Procharger in place, until the engine was blown and the rest now distant history......
PS: if your tranny is NOT manual don't even try!. 2 weeks is how long it will last!.