Can a creature apply any of their character's bonuses to attack rolls on an attack with a siege engine?
For example, if the person aiming a ballista has True Strike, do they gain +20 to their attack roll?
The Siege Mage archetype seems to indicate this isn't possible, given they can only add a small bonus by sacrificing a spell. But I'm not too clear on the rules for siege engines and attack rolls regarding what types of bonuses can be applied.
Did find a few relevant quotes from ultimate combat
"A direct-fire weapon uses a normal attack roll, with the
normal penalty for nonproficient use."
"Indirect Attack: To fire an indirect-fire ranged siege engine,
the crew leader makes a targeting check against the DC of
the siege engine. This check uses his base attack bonus,
his Intelligence modifier (if not trained in Knowledge
[engineering]) or Knowledge (engineering) skill modifier
(if trained in that skill), any penalty for not being proficient
in the siege engine, and the appropriate modifiers from
Table 3–12."
Based on these I would say yes on direct fire(uses a normal attack roll) but no on indirect fire(makes a targeting check not an attack). Sadly the siege weapon rules are written for NPCS