Ok, been trying to get forced roaming and this is what has been working for me. Get into epst mode, on my thunderbolt it is ##778 send! Go to modem settings change rev a to enable, go to cdma settings/ sys a primary should be set at 283 changed mine to 253 or 252 also and go to menu and press for commit. Phone will reboot. And from my experiences you have to be in an area where there is poor Verizon service. Then when phone comes on it will say on lock screen extended network= roaming.
Rooted with HTC Rom
Rf signal tracker installed
Open signal installed.... Do not know if these programs make a difference also have roam control but I don't even think that works on Verizon!
Hope this might help!