RTC support isn't implemented (yet) in Rockboy. Importing a save from an emulator that supports the RTC will make no difference since the loading code doesn't even try to load this part of the .sav. Unfortunately, this means games with RTC support will not function properly. So far, I've only heard of Pokémon Gold/Silver/Emerald as games using the RTC. Luckily, these games are still playable, however certain events will not occur.
I'm sure this is disappointing but most devs have little to no interest in Rockboy. So far I believe only a few developers have even touched the code. HCl did the initial porting effort and was the big Rockboy guy for a long time - it was his baby. Sadly, he passed away. Kkjurbun added support for color targets and scaling. He also improved the speed. I recently looked at Rockboy and pruned away unnecessary code. I also added support for small screen targets, preset palettes, and gained a small bit of speed. Other developers have contributed assembler optimizations as well.
RTC support is the big missing feature in Rockboy. Once that has been implemented, speed will be the only remaining issue aside from small, less useful features. Some work has been done to implement Dynarec into Rockboy. I've had a look at the code and may spend some time over the summer trying to finish it up. This may be optimistic since I'm only a first year computer engineering student and I've never touched upon Dynarec before.
Hopefully this long-winded post has answered your question about Rockboy and possibly some others that were lingering in your mind.