In the post linked below you can find links for a stock rooted/debloated rom of the 2.11.605.19 update as well as the radio that came with the update.
You can flash the rom in recovery, then flash the radio in the bootloader. If you need help with either of those procedures, you can check out my thunderbolt how-to videos on youtube linked below.
Link to Forum Post with Download Links
Link to YouTube Thunderbolt Playlist
