Sleeping bag alternatives please

My little one was born at 5.5lbs so could not have a sleeping bag to begin with and had to have a cellular blanket instead. By the time she was big enough for the sleeping bag, she didn't like it, so we've had the blanket ever since. The trouble is now she can roll, she rolls all around her cot including to the top of the cot, horizontally. With the colder nights coming in worried she's too cold as she wiggles out her blanket. She currently wears a sleepsuit and a vest underneath. I'm mainly concerned about her legs being cold as they have felt a bit chilly a couple nights. Does anyone have any suggestions for alternatives to a sleeping bag or blanket please?