The problem with starting free-roaming too soon is the potential for accidents. This is particularly likely once hormones kick in. Those hormones can cause excessive destructive chewing and can make them forget potty habits. You don't want him doing either of those since un-training is much more difficult than training.
I'd suggest waiting until several weeks after his surgery (to allow hormones to fully dissipate). To start free-roaming, it is best to start small. Limit his area around his cage initially. After days of good behavior in the smaller area, gradually increase it. Never start fully free-roaming all at once as that is more likely to cause potty accidents which (as mentioned) are much harder to un-train.
Don't rush it. There is plenty of time to get him fully free roaming.