I would be very surprised if Rohan turned positive so fast!! I cannot believe it.
Rohan has proven to be a vicous, cruel and aggressive person when thwarted. His first aggression (from the episodes i have seen) was when he suspected Radhika came to see Dev just before the marriage - he became like a maniac. Now this is when he knew Dev loved a girl in Rawal - he knew - and when he suspected that it was Radhika - he became a maniac - he did not care at the time that Dev and Rahika were in love - he got super angry. During the pheres he asked Radhika why she was crying and insisted that she told him the truth - he sounded like he would understand but when he heard that she loved someone else - he became a maniac again.
So it shows that he has anger issues and he becomes uncontrollable when angry.
So i find it difficult to accept that he could accept Dev's and Radhika's explanations and to reconcile to the fact that the two are in love and that it would be a sin to break that divine love. NO!! I think it is likely that he is BUYING TIME - he was caught out and he needs to reconsolidate and come up with another plan to make Radika his and perhaps to punish Dev forever.
I don't see any sense in leaving Dev and Radhika behind while he returns home to prepare the home front. Poor Dev and Radhika - they are so in love with each other that they grabbed any chance to be alone together.
I suspect he will cook up another story and Dev and Radhika will come home to a bombshell!!