The running backs were Lorenzo Booker and DeDe Dorsey, two guys who are known as scatbacks with good hands. Either one should be able to help in the passing game, especially. The tight ends were Tony Curtis, Joe Klopfenstein, and Leonard Pope. Pope is probably the best of that bunch, especially if they are looking for the explosiveness factor.
Working out running backs seems a bit odd, as they cut Dominic Rhodes before the season began. Rhodes, without much of an argument, would be a better option than either Booker or Dorsey. Also, they would only need a running back for the next two weeks because once Marshawn Lynch returns, he and Fred Jackson are a good enough one-two punch.
If the Bills are going to sign any of these players, it will happen later today. If they're not signed today, they most likely will have to look elsewhere.