It's elementary my dear Watson!

[Grimbold11]

I haven't used a "ball" spell effect in years and I can't seem to find the rules for it. The player casts the relevant spell (fireball, coldball, etc) and it strikes three targets. Does the caster get to add his agility or anything to the roll or is it a straight up roll and that's it? And do defenders get any DB bonuses?

Sorry for such a basic question!

[Sulimo]

It uses the Elemental Attack Roll (section 4.3 Page 42 of the RMC Spell Law PDF).

Basically, roll D100, add any appropriate modifiers, then consult the appropriate table for the type of Ball spell.

Page 42 (RMC Spell Law PDF, it's in section 4.3 of the FG Module Reference Manual as well) has specifics about your question:

AREA SPELLS
Certain Elemental Attack spells are called Area spells (Fireball, Coldball, etc.). These spells attack all targets in their radius.

Modifications to the EAR due to caster’s Agility, caster’s skill, and target’s shield do not apply; all other modifications do apply. There is a +20 EAR modification for any target at the center point (chosen by caster) of the spell’s effect, and there is a –20 EAR modification for any targets around the edge of the effect (i.e. their position places them at the outer fringe of the effect, perhaps even just partially within the area of effect.)

A GM may require only one EAR to be applied to all targets or individual EARs, whichever they deem appropriate for the given situation. If the GM decides on individual EARs, only the first could result in spell failure; a subsequent EAR that would normally result in spell failure is treated as a “no effect” result.

There is a pretty extensive list of modifications listed just before this section.

This is slightly different from the way it was handled in RM2 as I recall. There was a Skill called Base Spells, that could not be developed, but you could add the appropriate Stat bonus (based on Realm) to your D100 roll for these kind of spells.