RomanArmyTalk

I would like to create a roman calvary man. where is a good place to start?

I don't know if you could read german. If so M. Junkelmann - Die Reiter Roms is a good start.

There're also some good books on this subject in English, but I haven't seen them, so I don't what they are.

What period are you looking at? Our Late Roman cavalry is detailed on

http://www.comitatus.net/cavalry4.htm

and the links at the bottom of that page.

For earlier stuff, you could try Roman Cavalry Equipment by I. P. Stephenson & Karen Dixon, but I understand some regard it as pretty basic.

For earlier period cavalry try here