おもろい means “funny / interesting” (Kansai). Kansai squeezes 面白い (おもしろい) into おもろい. おもろ! is a clipped “that’s hilarious!”. The negative is おもろない, often squeezed further to おもんない (“not funny”).
Is おもろい rude? Who can you say it to?
With friends: OK. With coworkers: careful. With a boss or teacher: avoid. Kansai dialect. Casual.
How common is おもろい in real speech?
In 1,905 live comedy routines, おもろい appears in 72 lines from 26 comedians.