Romcenter

RomCenter 3.41 doesn't recognize the MAME Plus extra roms (plus, homebrew, decrypted, console).
I use M+GUI 1.5.0 - MAMEP64 0.137. It was the same by using 0.135 and 0.136 also.

I have Windows 7 x64 but don't think it's matter of OS.

Romcenter only recognizes roms exported by mame. Console roms list are not stored in mame like arcade roms. Use a nes dat for a list of nes games for example.
You can check all this from a dos command prompt : type mamep -list for a list of supported games.