What application can rotate a TIFF without re-encoding it?
GraphicConverter ($40 shareware) is the "Swiss Army Knife" of graphics applications.
The list of what it can do &amp; the file types it can handle runs to pages, far too much to even précis here.

The one thing it's very good at is 'not doing anything you didn't ask it to do' so for instance, it won't add an alpha channel if all you want to do is rotate an image.

Being "Shareware" in the good old-fashioned sense, if you run over the trial period it doesn't cease to function, unlike many other apps, so you can continue to use it until you decide it's worth your money.

No affiliation, it's just a cracking good product that I've been using for perhaps 20 years :-)