Hint: if splitting roundabouts ... about osm-relatify HOT 2 CLOSED

There is an automatic splitting system for roundabouts which consist of just 1 way. It is split at each intersection. The Relatify app already handles updating of other relations. Let me know if I misunderstood your question.

from osm-relatify.

for way_id in split_ways:
  way = id_way_map[native_id_element_ids_map[way_id][1]]

    # iterate over each related relation
    for relation in parents.id_relations_map[way_id]:
        relation_id = int(relation['@id'])

I think this will do the magic for the parents downloaded.
Thanks

from osm-relatify.