I am assuming that a Skirmishing ranger who uses a Scroll made for a Ranger, with the Ranger spell, say, Longstrider, what does the ranger do?
I'm pretty sure nothing will happen unless he uses a Use Magic Device Check.
This ability replaces the Ranger’s spells class feature. Skirmishers do not gain any spells or spellcasting ability, do not have a caster level, and cannot use spell trigger and spell completion magic items.
To use scrolls without UMD you need to have that spell on your class' spell list.
The skirmisher ACF clearly says that you loose anything related to spells... I guess it's safe to assume that a skirmisher has no spell list if he has no caster level and no spellcasting ability :-)
spell trigger and spell completion magic items = scrolls, wands, ...
So a skirmisher needs UMD to use scrolls and wands and similar items.