A beautiful feature of Openroute service is the capability to generate a round trip around a point given a certain amount of kilometers.
It would also possibile to affect the final result passing options like "I would a round trip that includes at least - so to say - 3 nodes (or ways) with the tag “amenity=place_of_worship”?
that’s currently not possible. You could pass the result route to the openpoiservice or search with it for relevant POIs and then generate a route between them.
Currently the roundtrip feature is basically a randomized route generator that generates a number of waypoints in a certain random direction based on the seed parameter.