Can you please advise if the baby lumo sleeping bag with sleeves is a safe product for my 4 month grandaughter? She has just begun to roll and sleeps for very short periods overnight I her own cot. Thank you.

Red Nose recommends the following:
A safe baby sleeping bag is constructed in such a way that the baby cannot slip inside the bag and become completely covered.
The sleeping bag should be the correct size for the baby with a fitted neck, armholes (or sleeves) and no hood.
https://rednose.org.au/article/what-is-a-safe-sleeping-bag

Red Nose does not recommend a specific brand of sleeping bag, but as long as it fits the guidelines above, it would be suitable.
It is important that baby is no longer swaddled once rolling, & a safe sleeping bag is a great option.