I agree with
@luuked that Bolden and Develin aren't a part of the "RB count" on the roster.
-- Bolden is, first and foremost, a special teamer who just happens to be a decent, dire-emergency RB reserve, too.
-- Develin is also a core member of the KR and PR blocking units, and, as a blocking FB, he's nearly certain to be on the roster regardless how many "live" RBs the Pats carry for the RBBC, or who they are. Also, since Solder has been lost, I think there's a better chance that "extra blocker" types like Develin (and Allen) will stick almost regardless because the new LT, whoever that may be out of the choices at hand, is likely to need the help.
So, we're really talking about 3-4 spots for "live" members of the RBBC. Whether that ends up being 3 or 4 doesn't necessarily depend solely on WHO they are and/or what different traits they may have, but may also depend on how many QBs and OL the Pats may want/need to carry in 2018. It seems likely that the Pats will acquire a rookie QB this draft and carry 3 instead of 2. Given the OT situation, they may also elect to carry 9 OL instead of 8. Both of these increases would, perforce, affect the roster counts at other positions, possibly including RB (or WR).
It seems that, for now, the Pats are still shooting for a 4-man RBBC (given that they're "interviewing" Hill and Woodhead). They have, IMHO, a good base with three solid contributors (Burkhead/White/Gillislee) who have NFL experience as well as at least a year's experience in the Pats offensive system.
While Gillislee's versatility seems relatively limited (so far), and while he certainly wasn't, in 2017, the dynamic runner that most fans expected (this could change in 2018), he's really not significantly more expensive than a mid-round rookie would be and his NFL/Pats-system experience may be worth the (+/- $1.5M) premium to BB.
If the Pats end up with 4 "live" RBs, Gillislle is certainly not a poor choice for the bench-depth guy who'll be inactive most weeks that there isn't an injury to one of the other three ... and that's assuming that (A) the Pats carry 4 "live" RBs, and (B) that the Gillislee isn't "promoted" to the active-3, with the new guy becoming the inactive bench-reserve in a 4-man committee. Anyway, it seems to me that an inexperienced rookie would need to be something pretty special to knock Gillislee off the roster entirely at this point. Could happen, but I wouldn't count on it.
WRT to Jeremy Hill - I'd be surprised if they sign him if his 2018 cap hit will exceed $2.5M. Given his 2017 performance, he might agree to stay under that on a 2-3 year deal. Woodhead, if the Pats consider him still capable, certainly fits the versatility profile and seems likely to sign for the veteran minimum. There are likely to be other potential NFL-experienced candidates out there (e.g., Zach Zenner - whose cost would likely be close to late-round draftee level), and - with three capable RBs now under contract, the Pats can afford to take their time sifting through the candidates and making a decision at this point.
