The ASRock board is Skt939 (non-SLI) with DIMM slots for DDR memory. It has an AGP-like slot for which you can buy a daughter card that carries a Socket AM2 and DIMM slots for DDR2. Using the daughter card makes the original socket and its DIMM slots inaccessible.
You are asking for a AM2 board that has both SLI and supports your Skt939 Opteron. The ASRock board is neither AM2 nor SLI. The change in pin layout from 939 to AM2 is principally to move from DDR to DDR2 memory support: your Opteron is only compatible with DDR, so why do you want an AM2 board? Why not just get a Skt939 SLI board?