This is probably an easy one for most of you. If a character uses prob control, who does he need line of fire to? It seems a little ambiguous to me.

Say you have just 3 characters, prob controller, attacker, and defender. And does the answer change on my turn vs opponent's turn?

He needs line of fire to whoever is rolling the dice.

The character using Probability Control needs to draw LOF to the character that is making the die (dice) roll.

Probability Control
Once during your turn, this character allows you to reroll one of your rolls, ignoring the original roll. A character using this power must be within 10 squares and line of fire to the character for which the original roll was made. Using the same rules, once per round during an opponent's turn, this character allows you to force that opponent to reroll one of their rolls, ignoring the original roll.