The miner needs to verify the entire block chain history because otherwise he has no way of knowing if he is actually on a valid chain or not. This has nothing to do with UTXO commitments, rolling root, or any other proposal. It's a basic, fundamental requirement of any consensus system: if the miners themselves operate in SPV mode (which you advocate)
Full stop. I have never advocated that. If you believe that, then you never understood the rolling root proposal.
I agree it's best to keep the threads separate. If you have questions about how rolling root works feel free to ask in the other thread.
Sticking to UTXO though, I don't believe you answered my question. UTXO is not SPV either, so it is still not clear to me why you say they don't know whether they're on a valid chain or not. They downloaded the headers from genesis (SPV), but in addition to that they downloaded the entire UTXO meta chain which they can then use to verify any txn and build the merkle/btree or w/e the latest data structure is.