Even before the Bills hired an offensive coordinator that emphasizes tight ends and fullbacks in his run-oriented personnel packages, Buffalo had a fairly significant need to draft a tight end.
The Buffalo Bills probably won't have much playing time to spare for any rookie running back or wide receiver that they pick up in the 2015 NFL Draft (though they could certainly make room if necessary), but that is not the case at the more blocking-oriented skill areas in the offense Greg Roman will be installing in Buffalo.
Buffalo entered the free agent signing period knowing that they'd need new athletes in full-time roles at both tight end and fullback, which is why they released four-year starting tight end Scott Chandler, then gave veteran players Charles Clay and Jerome Felton high-end contracts at their respective positions.