First; did Ser Forley Prester send any part of his 4000 men at the Golden Tooth to Ser Stafford Lannister at Oxcross, in order to augment his host? Or were they all kept at the Tooth by Prester?
That's much too big a garrison for a small castle like the Tooth, so I expect that he sent many of them down to Ser Stafford. Blooded veterans to help train the raw green levies... of course, that didn't work out too well...
Second; what did Robb do with the Tyroshi sellsword who dipped his banners at Riverrun?
I don't know what Robb did with him... but =I= forgot all about him, I blush to admit.
Now that you've reminded me... I imagine he kept most of them with him when he went west. Having just marched through the westerlands when they were on the other side, they would have had a certain value.
I also would expect that he suffered some desertions... these men were not bound to him by oath or ancient loyalty, and there was plenty of plunder to be had...
There's at least one Tyroshi outlaw in the riverlands in SOS... good chance he was a deserter, although whether it was Jaime or Robb that he deserted, I couldn't tell you right now...