As mentioned before, The Purple Crystal allowed the twins' group cultivation to reach a level similar to the Semi-Celestials. As long as they are in this world, they won't be weaker, at the very least. Yet, Roan was making quick work of that Wonder Beast, something that Sansara and Black Locust had to join forces to achieve the same result.
Why? That's because Sansara and Black Locust refrained from using their Semi-Celesital powers of controlling and changing the laws. Only when the Semi-Celestials are in that state would they similar in strength to Roan. Obviously, Roan doesn't need nor can he change the laws, but his Chaos Cultivation definitely made up for that.
Meanwhile, Sansara finally spotted the twins' group, focusing on Kafan in the distance. "Kafan, help me!"