Should I reroll the winner?

I would re-roll and report him/her

Im guessing he entered both giveaways at the same time, so not really his fault for winning both giveaways.
Since he already won the game it is a valid reason to ask for a reroll

If you should ask for a reroll or not is up to you, but you definitely can.
If the infraction is less than a month old the reroll will be granted anyway, regardless if they were suspended or not.

You will never bother support with multiple win reports, it's their job :)

It´s up to you if you want to re-roll. If this guy has more than one multiple win i would re-roll. But everybody makes mistakes sometimes so if it´s only one i would talk to him and ask what happend. Some people don´t hide the games they already own and then enter and win giveaways by accident and end up with a multiple win. Of course it´s their fault and it should not happen but who is perfect. If a mistake happens only once then it´s okay at least to me as long as there are no other issues like unactivated wins. The way the rule breaker reacts when you talk to him can give you a good impression of his attitude. Some are respectful and apologize others get angry and some just don´t no about the rules. People can be very different so there is no simple answer to your question.

Support said themselves several times on the SG discussions that when in doubt, make a ticket to be sure.

Ask for a re-roll. If he\her already served punishment then you won't get it. If he\her hasn't been suspended yet, he\her will be suspended and you'll get the re-roll.

When in doubt, file a ticket with Support.

As your issue has already been dealt with, you are free to close this thread whenever you wish.