Hi, My 3 month old has started wriggling in her bassinet so she's up against the side or turned 90 degrees. She's not yet rolling. She's in an ergopouch sleep suit with arms still tucked in as she wakes herself a lot with them out. Head control is poor although we're trying a lot in tummy time. Our room is too small to have the cot in it but we would really prefer to keep her in our room until around 6months. Would it be safe to put her in a portacot at night for a few months?

Many babies will wriggle & squirm in the bassinet when they are trying to learn to roll, especially by 3 mths of age.
Most babies will be rolling by 4-5mths.
It is important for most babies who are wriggling like this, at this age, & when in a bassinet & swaddled, should be moved to a cot, as they may be at risk of getting stuck in an unsafe position if/when trying to roll.
Babies need space of a cot & arms free to roll well.
Tummy time is very important for building upper body muscles to assist with rolling ability.
Rolling is not something that needs to be stopped but continue to make her sleep environment as safe as is possible.
Have a read of this article: https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

Portacots are generally recommended for use as a temporary sleep environment
https://rednose.org.au/article/portable-cots

See also the info on Room Sharing which includes:
“Parents are not expected to observe their baby constantly. If your baby is sleeping in a separate room check baby regularly to ensure that the baby remains on the back and the head and face remain uncovered.”
https://rednose.org.au/article/room-sharing-with-baby