My baby is 5 months and is able to roll back to front and front to back (only rolling awake l, has not rolled in sleep yet). The cot is too big to fit in our bedroom and I don't feel comfortable just yet to have baby sleeping in their own room. Because of this I have had them in the portacot for the past 2 weeks (since they mastered rolling). My plan is to move them into the cot in their own room as soon as they roll in their sleep. Is it safe that I am currently allowing them to sleep in the portacot at night? Or should I move them to the cot now?

Thank you for your update on your baby since he was 12 weeks old. The same information applies whether your baby is rolling when awake or asleep. It is about them having the physical ability to roll.
Most babies will be rolling over by 4- 5 months. Some earlier, some later.
This is very normal as babies grow & become stronger.
Many babies then prefer to sleep on their side or tummy.
This is not something that needs to be stopped. It is important to make his new environment as safe as possible.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

Is he increasing his activity during tummy time?
The portacot can be suitable for short term sleeping, but would definitely suggest moving him to his permanent (household) cot at 6 mths of age.
Have a look at the information about use of portable cots from Product Safety (ACCC) & Red Nose - particularly about when to stop using & the importance of checking that there is no wear & tear.
https://rednose.org.au/article/portable-cots
https://www.productsafety.gov.au/products/babies-kids/kids-furniture/folding-cots