Well, my baby, Hootie, she is 5 months old but I don't trust her to roam the house bc I am not convinced she is 100% potty trained yet. And, she cannot jump on/off the couch yet, so I don't want her to get hurt while I'm gone trying to do things like that.
My oldest, Hobbs, he's 1 year and fully potty trained and I fully trust him so he gets to stay out and "roam free." I do keep the bedroom and bathroom doors shut, so he really only has access to the kitchen, living area, and foyer.
I will let Hootie stay out, too, when I am convinced that she is 100% potty trained and when she can jump on/off the couch and when I can trust her not to get into any trouble!