Yes those Roots III sources will transfer fine, according to Bob Velke, TMG owner/programer.
Just about everything that has been suggested as 'cleanup before GenBridge activity' has already been taken care of in the TMG 4.0a TMG GenBridge transfer program.
When you receive TMG 4.0a, install it and import a project using the TMG GenBridge utility (NOT GEDCOM). Then spend all the time needed to explore your data in TMG. I believe you can correct most anything using either TMG or UFT. Since you will be more familiar with UFT, it may be easier to correct there. When you are satisfied at the correction job you have done in UFTree, delete the TMG project and reimport via GenBridge into TMG. Importing UFTree project(s) into TMG will not affect the UFTree data. It will still be on the computer, in UFTree, unchanged.
I plan to very carefully study and follow the TMG instructions about importing. I suspect spending a month or two studying the TMG program and comparing the TMG data with the UFT data will be time well spent.