Yuen Biao, being the lesser known from the 'Three Dragons' (Jackie Chan, Sammo Hung and Yuen Biao) hasn't starred in many classics that doesn't include his more famous friends. 'Rosa' is one of them non-classics. Yuen Biao is equally capable martial artist and actor as his internationally known compatriots, so is Kara Hui, but both of their abilities weren't fully used in this quite trivial action comedy. The film is quite entertaining, and there are some fine fight scenes, but some of the slapstick bits are drawn too long and start to get annoying by the end.
This movie is only worth to see if you are a huge fan of Yuen Biao and/or Kara Hui (they both have done some more amazing movies), but in every other sense 'Rosa' is barely above average time filler.