Nice effort user, thanks for that.
I had intended Leader to really be more-or less "the independent character Role", but it's definitely removal for any time of Consul that can't be a compulsory HQ choice in the current FO chart. Part of the perk of using Leader as a Role is the ability to take Leader detachments, with each Leader as a different subrole. Leader detachments could have some kind of superbubble if all the Leaders are within 6" of each other.
Definitely Spirit I'd say, Bolster is quite a broad rule I had in mind for any unit that boosts others in a general or baseline sense, while maybe not fitting into other setups.
Centurions are meant to be highly flexible and really could turn up in all kinds of lists, so I'd move towards giving them 4 Roles minimum.
This reflects their general purpose nature and the fact that they lead forward-lead small parts of larger armed forces.
Replace all four default roles with Psyker and Bolster. Librarians are very rare units that should feel difficult to include in an army, especially en-masse. Changing a Librarian's wargear might not affect their Roles, as they are already predominantly defined by their Psychic powers.
Master of Signals
Replace all four Roles with Communications, Rifle and Cannon. Even though MoSs don't carry these items themselves, they naturally synergise well with them, so they'll turn up in the same formation as them.
Replace Leader and Battlefront with Duellist. I'd also include a special rule in the unit that lets it be taken as a support unit (Retinue) for another model with the Leader rule, adding Duellist to their Role set.
Replace Melee, Battlefront and Patrol with Engineer and Construction.
Replace Melee, Leader and Patrol with Medical and Bolster. Again like Champions, let them be taken as a retinue for a Leader, granting the Medical role.