I had this originally running on my supercard. Noticed your post and tried it on the R4.
Works ok. Obviously your .st game images are oki doki if you have tested them on the mac.
I´m using the tos 102 uk which is regarded as the most compatible for most games.

Can you boot to the TOS GEM GUI?
Can you see the roms in the file browser?
If possible use single game .st and not multi game menus as most of them use packers and this can cause the emulator to hang.

This is the way I load em up.
1. power up emulator.
2. press right trigger to bring up autostart rom image menu.
3. pick an image upsing d-pad up/down
4. press a button to load rom.
5. some games require a keypress/mouse click to continue loading after splash screen. Others will boot to the TOS Gem GUI where you will have to navigate to the game executable and double click to launch.

Please not that some games take quite a while to load. So be patience. Always check to see the disk access icon is flashing or the cpu load reading is fluctuating as a guide that emulator is processing data.

Quick n dirty test on the R4.
Rick Dangerous.
The Sentinel.
Dungeon Master.
Oids.