IMO the signings of Hoecht, Jonah Williams, and Rozeboom are significant because I can see where these guys can push for a roster spot next year because of the handicaps they faced with the virus restrictions. Also, they provide important depth at key positions this year in case of COVID roster losses. Hoecht, is a far better DT than SJD and if SJD continues to get blown off the LOS it should be a time for a change. Williams was someone I expected to make the roster and still might. He's very close to what you want at DE or SAM. But I agree that Hollis is a better choice this year as he brings experience and positional flexibility, especially behind Ebukam.
Rozeboom has a shot to fill that second ILB spot next year if it remains unsettled. At least he can potentially provide good depth behind an established starter. He has decent speed for the position, enough to play sideline to sideline, but he also plays fast, able to read and react quickly which is testimony to a player who preps well. He understands zone concepts and has enough speed to execute it, meaning he shouldn't be a liability in pass protection.
They have one spot open I hope they bring back MacGinnis if he hasn't signed. The kicking game worries me.