@hexxur i know there is away to get retroarch installed on it. and i know that it have a doom port built in.
how it works with WADS i dont know

Zandronum scriptmodule has now been updated with support for registered versions of Doom, Doom 2, TNT and Plutonia wads.

Just copy the 4 wad files to the doom roms folder in "/home/pi/RetroPie/roms/ports" before installing Zandronum.
This will give you 4 new runcommand files to launch the games from.