Extra info:
Left it run for the night, come back the following morning, U3 isn't running. Go and have a look, seems that the power brick burnt out. After getting in contact with the store, they tell me that the frequency was set too high and that's why it was running slow and overheated the power block. Since I see no way to set the frequency in Minera, he recommended me to use MinePeon, or directly from the PC.
My thing is, I tried using MinePeon once, but the Rockminers don't seem to like the environment and thus don't work.
Any ideas people? The guy from the store recommended for me to use it via the PC otherwise, but then that defeats the purpose of me having the Raspberry Pi...