By era I guess u mean this decade...
Roger's trained few fighters. Mainly Floyd.
Mayweather Sr. trained Oscar and Hatton notably.
McGirt hasn't looked good with his fighters of late(not that its his fault).
Naazim's only really worked with B-Hop. I'm not buyin that win by Shane, since Margarito was tailor-made for Shane anyway.
Roach has mainly only worked with Pac this decade
Emmanuel's had success with Wlad and Lennox
Not really a clear answer IMO...I voted Steward
http://static.guim.co.uk/sys-images/Sport/Pix/pictures/2008/11/20/1227216143920/Ricky-Hatton-and-Floyd-Ma-001.jpg
Floyd Joy Mayweather Sr...not the greatest of this time, that time, but of ALL-TIME!
Honestly maybe Emmanuel Steward, can't think at the moment.