We had a twin and it was huge. Definitely room for a rollaway bed as there was a seating area.
Best to go for 2 twin rooms - 1 for two and 1 for three persons. I believe, unfortunately, the hotel does not have rooms with connecting doors but will assign adjacent rooms or rooms close by. Request the rooms at time of booking.
Enjoy your stay in Kyoto. Granvia is our first choice for the location and comfort.
If cost is not an issue, go with twin rooms with separate beds. I don’t know if they have triple twin rooms.
We were only 2 but I would suggest the suites- they were quite large
Get an answer from Hotel Granvia Kyoto staff and past guests.