Hi
No need to worry about rolling over. Rolling over from prone to supine comes at around 24 weeks and supine to prone at around a month later. He is only 12 weeks. As per your description, development seems to be normal.
Next Steps
you can also check if in prone position he is able to lift his chin and shoulder off the couch with legs fully extended which is usually present at 12 weeks.
Health Tips
no need to worry. he will achieve development landmarks at appropriate age.