30 second+ is higher than expected but you will see sync issues with people with high pings. Roll20 uses a central server to coordinate state so it would be reasonable to see a delay of: (2x your ping) + (2x his ping) due to the round-trips that need to be made between each client and the server.
If you see this again please post the date, time and timezone it happened. We can the check if the hosting provider was having issues at that point in time to help figure out the problem.