Analog film photography and cameras

I was actually metering with my digital camera, but the light was just so variable I guess.

Hard to say what's going on from here.
Could be bad scanning as well? The middle castle picture looks weird. Are the negs all over the place as well?
Those at the sea you posted above look fine, exposure wise - or did you get really bad ones there as well you didn't post?

Another thing that came to mind is the t-stop of the rollei being quite different to the one of the digital one you're metering with.. though can't imagine this making more than one stop difference..

I'd sacrifice one roll (shot with various speeds and controlled lighting) to really get to the root of the problem..