if it is coming from the side walls you should see some damage on the walls also.. softness of the luan..We had a slight crack in one of our seams and water was coming in from the roof, running down the sidewall above the door and window by the table (mostly the front passenger side) so we have some interior work to do and it is next to impossible to find the same wallboard to match the original..
last but not least,, a new roof is in the near future.. not cheap
good luck