It was the idler pulley that tensions the belt. Ordered the repair kit from AppliancePartsPros, it came in 5 days, would have been less but for a huge snowstorm day before delivery date. During those 5 days I used their video to help disassemble the dryer. Worked like a charm, even though the model was very slightly different.
I was very nervous, but following the video helped. I also put each set of screws into plastic baggies and labelled them, just to make sure I knew the order of the steps. I cleaned all the lint from the inside of the machine, looked SHINY! Use a vacuum, handheld, if you can.
When the parts came, I was able to replace the rollers, idler pulley, and belt in short order. Reassembly took about 90 min because of a slight difficulty with the bottom housing panel.
Total time spent on the disassembly/assembly was about 4 hours, but it was my first appliance repair job. I am sure right now I could do it again in 1 hour if I had to. Not that hard, just...mysterious :)
TY AppliancePartsPros!!