I'LL JUST BORROW THIS, SUGAH: At the beginning of the game, choose a standard power another friendly character can use on its starting click. This game, Rogue can use that power and, when she does, she has the printed range value of that friendly character.

HIDDEN PERSONALITIES: Give Legion a free action and choose a standard power, then roll a d6 that can't be rerolled. He acquires a "Personality Quirk" from the table below, and uses that and the standard power until your next turn.
1: "Cowardly" Legion modifies his attack value by -2.
2: "Confused" Legion modifies his speed and defense values by -1.
3: "Grounded" Legion can use Earthbound/Neutralized.
4: "Enraged" Legion can use Battle Fury.
5: "Compassionate" Immediately heal all adjacent characters 1 click.
6: "Savant" Legion modifies his combat values by +1. Choose another standard power and he can also use that power.

My question is as follows: if I am teaming Rogue and Legion together, can I have Rogue choose any standard power since Legion's trait allows him to use any standard power of your choice on his opening click.

Legion has a special power. It allows him the ability to use standard powers with a free action, but he can't use them standard on his opening click. If there were not an activation tied to him selecting a power, there might be a way around this.