Roof leak in rear bedroom, 1979 FC 35

[Henry Claeys]

(1) There's a roof leak on the driver's side of the rear bedroom, between the
cabinet and the wall, in front of the window but before the closet heading
forwards. (2) Are there any characteristic areas I should look into to locate
the leak? I climbed up on the roof but did not see any obvious places for the
leaks, other than the screws in the roof. Everything inside, including the
cabinet, is dry, but the wood strip, along the length of the cabinet and
directly between the cabinet and the wall, has water marks on it. (3) Any
advice appreciated. Henry@... 1979 FC 35, McAllen, Tx.