I think that 15 months is about the minimum for a toddler to go into a toddler bed....I seem to recall reading that somewhere.

We got a toddler bed for Jacob when we were expecting Ruby and he is like Owen in that he rolled around the cot a lot. As a result, the toddler bed just wasn't for him as he ended up on the floor in the middle of the night! He wasn't upset at all about going into it - he thought it was exciting as it had Pooh Bear on it! Mind you, he was somewhat older at the time. Anyway, we ended up ditching the toddler bed and putting him into a single bed with a bed rail on it - this has proven to be MUCH better for him, as he still rolls and throws himself about in his sleep a lot! We have a bed that is quite low too.