Is there any limitation of room list distribution group?

Yes, there is a limit of 99 (less than 100) in a Room List in Outlook. This limit does not apply to OWA.

https://support.microsoft.com/en-hk/help/4041212/can-t-view-available-rooms-after-selecting-room-list-in-office-365-ded

This limit appears not to be the number of rooms in the room list but the sum of the attendees and the number of rooms.
93 rooms + 6 attendees works fine
93 rooms + 7 attendees hits the limit.