〜やろ means “right? / come on!” (Kansai). Kansai swaps だ for や, so だろ becomes やろ. おかしいやろ! = “that’s ridiculous!”, one of the most common Kansai comebacks.
Is 〜やろ rude? Who can you say it to?
With friends: OK. With coworkers: careful. With a boss or teacher: avoid. Kansai dialect. A firm やろ! is a comeback; a soft やろ? just checks.
How common is 〜やろ in real speech?
In 1,905 live comedy routines, 〜やろ appears in 689 lines from 92 comedians.