If you're looking to save money, a roll back especially a Linhof Rollex will add a lot of expense, with not so much benefit. You can buy a lot of film and holders with what the Rollex will set you back.
For the 4x5 frame, you probably don't need to go wider than the 90, and for a first lens, you're probably better off with something a little longer. The 90 is fine for wide sweeping vistas. But it's awfully short for most anything else, though tastes vary.
A lens like an SA 90 is also expensive compared to something in the 130-180 mm range.
The longer lens will let you use the camera's movements more effectively, and you won't run into constraints of running out of bellows at it's minimum.