Hey man, sorry I haven't responded to your PM. Here's how it pretty much works:
So the roster files that are out now are designed for the PC and all of the latest cyberfaces. A cyberface is what gives the player his "real" face. The rosters have an ID number for cyberfaces, ranging from 1-900 of current MLB players and managers. These are stored within the models.big file. If none of the guys on this site create a cyberface for that guy, he is assigned a generic face ranging from 901-915.
If you check your models.big using biggui or EAGraph, you will notice that there are gaps between c001.fsh and c900.fsh. These are the cyberface files and the gap means that that cyberface doesn't exist in your copy of the game. When you import a PC roster, it will be expecting, for example, c416.fsh to be in your models.big. But Alexi Ogando wasn't playing when MVP 2005 was made, so his face is not included. The listed cyberface in your roster that does not have a corresponding file in your models.big will cause a crash. Only players playing in 2005 will have cyberfaces in your game. So, any players not represented in your models.big will have to be changed to a generic cyberface by using MVPEdit to correct your roster set.
You CAN use the standard maker to exchange most of the faces to generics. However, it might be better to just do it manually or there will still be errors, such as a random minor leaguer showing up with Roger Clemens face. It will be quite a bit of work. Don't forget to edit the managers as well.
My best suggestion honestly is to just bear down and pick up the PC game. It's SO much better and easier to work with, plus the classic mods are amazing. I just got it a few months ago and now I think I can finally let my old XBox rest in peace.