Is round trip ticket is required?

Yes, the round-trip flight ticket is still required when they apply for tourist visa "L" in the Philippines, I don't think you can get a residence permit for your family in China. If you are a Chinese citizen living in China, it is possible for you to do so, however, you are a Filipino working in China, if you want them to live with you in China for a long time, they should apply for a dependent visa (Z visa) in the Philippines, they don't need to provide round-trip tickets. After entering China, change Z visa into residence permit.