How is caster level determined when using scrolls?

[NegativeZero]

Like for example if I have a level 11 sorc with + 15 magic device using a fireball scroll (a spell she already knows) vs. a sorc spell she doesn't know vs. a cleric spell

[Kommissar K]

Minimum caster level/minimum stat to cast for making the scroll. So for example, a scroll of a 1st level spell is going to be cast as if by a 1st level character, with a stat of 1 for the DC (so DC 12 total).

Your own character has nothing to do with it. Its baked into the scrolls creation. If Scribe Scroll was in the game, you could choose to pay more when creating the scroll, but that is a specialty decision vs. just buying it from a store (technically in tabletop, a store could sell a scroll at a slightly higher caster level, but it would be priced accordingly).

If its a 5th level wizard spell, its minimum level 9th, with a minimum of +5 in the casting stat, so its going to be a caster level 9, DC 20 effect.

I would assume the scrolls in this game are made using Wizard/Cleric spell lists, as those are often the earliest/cheapest.

[Lord Koth]

If the spell is on your spell list, you're not using UMD at all to cast it. Either you just cast it, or you make a caster level check against the caster level of the scroll if it's of a higher spell level than you can cast.

And speaking of scroll caster level, you ALWAYS use the minimum caster level of the scroll unless you're a single specfic wizard archetype. It doesn't matter whether you're UMDing it or casting it automatically due to it being on your spell list. So that FIreball scroll will always be cast at CL 5 (it's a 3rd level spell, which means wizards get access to it at 5th level).