I'm sure the team would be pleased if Brent is able to return as a productive member of the team. If not, though, I feel he should be treated as anyone else would, regardless of his having been a player previously. He's served his debt to society. That being the case, he has the right to be treated as any prospective contributor to the organization. The FO surely must realize they're not a charitable organization and must treat Brent without any bias as a former player nor resentment for having violated the team's rules in the past. He should be a prospective player like any other with no special considerations.
If Josh is able to return to being a capable and productive contributor to the team, by all means, he should be rehired, regardless of his former transgressions. Of course, there's also a likelihood that the time off in incarceration has taken its toll on his athletic abilities and conditioning. I imagine the staff is well aware of that but will allow him the opportunity to regain his former conditioning as much as humanly possible.
If he's able to accomplish that, then welcome back. If not, he should be dismissed like anyone else would who isn't able to pass muster. Personally, I wish him well and hope he's able to contribute once again, although I'll admit being somewhat unsettled as to whether or not he'll be a good fit within the scheme that's in place with Marinelli. In any event, I wish him well in the future, whether it's with the Cowboys or possibly some other team.