"Scrollery": I'm not sure, without knowing the context; but it may relate to wood-carving in the form of a scroll.
"Sheep-gazed neatness": this appears to be the author's own coinage. Again, it's difficult to tell without context; but it may mean "a tidy area overlooked by sheep" (!). Alternatively, it may be a typo for "sheep-grazed neatness", which would mean "an tidy area of grass which sheep have grazed".
"Scutched": this may mean "struck with a stick", esp. in the context of striking corn with a stick to obtain the grain.
"Rosebay willowherb": this is a tall plant with attractive pink flowers (Chamerion angustifolium), often grown in gardens in Victorian times, incl. in white forms, and common in the English countryside since the Second World War, though rare before (it particularly liked bomb sites and railway lines, and spread rapidly after the war). It's a member of the family Onagraceae, and so is related to fuchsias (though it doesn't look like a fuchsia).
Here's a picture of it in a characteristic location.
"Expiation": atonement for a sin or other offence (either in a religious context, or metaphorically).
Where did you find these unusual words, out of interest?
All the best,
Interested in Language