Note: the damage here is generally trivial, and this question is mostly silly, but now I'm curious and would like to see if anyone knows of any specific rules or official rulings on this.
Imagine the following scenario:
A character with a spear (2H Simple Weapon, 1d6, x2), 12 Strength (+1 Str Modifier), and no other damage bonuses. They roll a crit. How high is the total flat modifier for the damage on this crit?
Theory 1: Round immediately.
This seems to be the common camp, where one rolls 1d6 (base weapon damage) + 1.5 (1 Str modifier * 1.5 for wielding two-handed), rounds down to 1d6+1, then rolls a second time for another 1d6+1, total of 2d6+2.
Theory 2: Round at the end.
While apparently unusual, this case is perfectly valid by the rules, and may be closer to RAW, though not RAI. Here, you roll 1d6 + 1.5 + 1d6 + 1.5, then add them together for the total crit damage of 2d6+3.
The rule is clearly round down when you must (in the PRD, that's actually "are must", but I'll let that go for now). That isn't a problem. The rules for adding up multiple "damage rolls" for a crit (rather than "multiplying") is also not a problem. The question is: when must you round down? Specifically, can someone find a direct quote from the rules that state you should be rounding down before determining final damage on a crit?
Ok, now the above character is: Wizard 3 / Magus 1 using Evocation's Intense Spells on a Shocking Grasp delivered through that spear, without getting a crit against an enemy with no resistance or DR.
This yields: 1d6 + 1.5 (physical damage) + 1d6(3d6 if cast with wizard slots) + 1.5 (electric damage)
Rounded down immediately because they are separate types of damage with a +2 flat modifier, or added together for a +3 flat modifier on the rolled damage from the attack?