The noun (and verb) rollback on Stack Exchange means to undo or reverse an edit. I'm not sure if there is a difference between the two, but that's how I understand it.
Recently, I posted the past participle rollbacked, in a comment, and after a bit I looked at it and realised I should have written rolled back.
The problem is that rollback is spelt as one word, so adding the suffix -ed was an automatic gesture. And if I think about it, backed is an adjective, and back is also a verb. Here's another example, double-click, is the past tense doubled-click or double-clicked?
Was I so wrong to write rollbacked?
Why should it have been rolled back (two words)?
Are there cases of compound nouns (and verbs) where either the first noun/verb or the second can be placed in the simple past tense with no changing in meaning? I can't think of any on the top of my head.
Best Answer
Tenses always apply to verbs, so to see where to apply it, you need to figure out which part of the compound (or hyphenated) word is the verb.
"Rollback" is a compound word, consisting of the verb "roll" and the preposition "back", as Peter indicated. As such, "rolling" is what you are doing, and "back" indicates where you're rolling (as opposed to rolling forward).
"Rollbacked" would imply that "back" is the verb, as in "to support". Unless you're supporting the edit with a cinnamon roll or used said cinnamon roll to move it back, this is not correct.
A converse compound word would be "backup" -- here, "back" is the verb and "up" is the preposition (see the etymology of 'backup' in its non-compounded form). You haven't "backupped" the files, you've "backed up" the files.
With regards to double-click, "double" is the adverb that modifies the verb "click", so "double-clicked" is the correct form. I can see this possibly being confusing because it could be seen that you're "doubling" the click (or past tense, you "doubled" the click); however, when you tell someone to single click, you just say "click the button", and thus it becomes more obvious that click is the verb here.