A collection of brand new and barely used filters, a brand new dust bin, brand new brushes.
The tinkering was fun as long as it produced results and I think I got pretty good at it. I could break down a Roomba and expose its guts in about five minutes. Opening the gear case took another five minutes. I affixed the bajillion screws to a strip of masking tape in a relevant pattern so each one ended up back in its original position when I put the robot back together. I know where all the failure points are and what to do about them.
The last two Roombas broke my heart. I took one of them apart twice for gears. No joy. I took it apart again for a brush drive motor. Silly me. I took it apart one last time for a vacuum motor. Still doesn't work. I went to work on the other Roomba. Took it apart for gears and again for a brush drive motor. Put on a new dustbin (where the vacuum motor lives). When that didn't work, the Roombas sat on the workbench for weeks. I couldn't face them again. The mess finally got to me, though, so I disconnected the battery chargers and hung the robots on the wall, where they will reside for their foreseeable useless future. Patience has limits.
Sell them on eBay for spare parts? Ha! You'd be amazed how many sources of Roomba spare parts are on eBay. Laurie suggests I take them to the vacuum cleaner repair guy downtown. Maybe I will. Let somebody else have all the fun for a change.