The deadline to make changes for the next scheduled round of a tournament is 2:00 a.m. PT on the morning of the round. If you don't make any changes, your active foursome remains the same for the next day.

You cannot make any roster changes on Sunday after the 2:00 a.m. PT deadline passes.

Is the roster deadline adjusted if a round is delayed or suspended due to weather?

No. The deadline to set your lineup for a particular round is based on the original tournament schedule and does not change even if there is a delay to the start or finish of a given round.