So what happened to the Tully forces?

[MoreOrLess]

My guess would be that Edmure commanded his men to obey the Frey's and was then taken hostage again to make sure they kept to it.

They could have Ayra free Edmure or they could have her ignore him either out of ignorance or showing that she is too revenge focused. If she does the former then maybe she works with him to help free the Riverlands or maybe others in the area or Sansa do. if she doesn't free him maybe others do or perhaps the Lannisters actually deside to? The Frey's were incompetent and commanded little loyality plus have just had all there experienced leaders killed, restore the Tullys(who would command much greater loyalty in the Riverlands) and maybe take Edmures son hostage to make sure he supports Cersei.