You need to create him in game and do some dbf editing. Every lines that are in Live 2005 roster you can copy.
Here you have a guide of editing players.dbf file and
here for appearance.dbf.
You will need also to import his face from Live 2005 using EA Graphics Editor which you can get
here. You will need to open plyrface.viv under NBA Live 2005/sgsm/players with this program and export lasprew.fsh to you sgsm directory in Live 08 folder.
If you do it right, there should be no problem. If you will have any problems, write to me and I'll try to help you.