Congrats to you ~ I am a PROUD SAHM to 3 year old boy/girl twins! Our went to toddler beds at 18 months and then to twin beds before they were two. They rolled out of the toddler beds a couple of times and their twins beds a couple of times, but otherwise we have had NO issues. I did not like the standard rails that most parents use on kids beds for safety. Instead I put one side of their bed against a wall and then for the other side, I used a rolled up bath towel (put a rubber band over the end to keep it rolled up... it'll look like a giant tootsie roll) and slid it under the fitted sheet to keep it in place. You can also use a swim noodle and cut it to fit the length of their bed. It is just a gentle reminder for them to roll over on their own. It takes greater effort for them to roll up and over the roll than to roll back the other way back into the bed. Make sense? I just recently (just after their third birthday) took the roll out/off their bed. My daughter has rolled out once, but I believe it was because we had her sleeping on a wedge to ease her coughing due to a severe cold. She rolled off the wedge and then right out of bed ~ she let out a "Mommy" at the top of her lungs, but when I got to her she was perfectly fine!! It startled her more than anything!! I got her settled right back in bed and she was fine!
Liek other mommies said, I would also suggest finding something else to "contain" your kiddos like child gates or play yards rather than their beds.
I might also suggest that you give them ample activities in which to climb. We have always had a climber of some sort so that they were never led to jumping/climbing on couches, beds, etc. that were unacceptable places to jump or climb.
If they were ever inclined to do that, I just reminded them that that was unacceptable and ask them where they were to slide/jump/ or climb. They always answered "the joey slide" and went right to it to continue their game/activity!
I know I have started to ramble, but I hope I have given a few suggestions to help you.
Take care!!
C.