Awhile ago, someone made a thread referring to the duoing in ranked on League, about how the duo always got first and last pick. They're actually changing that now, so someone will always be first pick, and the second person will be randomized. This means you can both be at the top. This is all copy pasted from the League of Legends patch notes.

With the deploy of patch 4.2, we announced the below change to Leagues but did not enable the feature until today. Weve since turned it on in North America only. We expect it to roll out to other regions next week.
The below changes will be enabled today:
All players will now have an equal (random) chance of being first pick
For players in a duo, if either player is chosen as first pick, the team captain will be assigned first pick and the other member of the duo will get whatever position the captain received from the randomizer
In solo queue matchmaking the difference in skill from top to bottom is too small to justify a pick order difference in champ select. This change will make it more likely for all players to have an equal shot at playing their favorite role. It will also remove potential duo abuse cases; a randomized order makes it completely fair for pick order regardless of whos queuing with whom, and reinforces our core focus on communication and collaboration at champion select.