I am the room leader in the baby room and I have had a few parents have their child/ baby that's less then a year old sleeping on their side or tummy. What is the appropriate age or months that children are able to sleep on their tummy or side. We follow the Red Nose guidelines as well having all babies sleep on their backs. But would like to know so that I am able to understand and share with parents the importance of their child's sleep.

Red Nose recommends baby is always placed on their back for sleep.
Most babies are rolling by 4-6mths of age.
At this time, still place them on their back for sleep, but allow them to find their own sleep position. (thids is often on their tummy)
Babies who are rolling, should not be swaddled.

Red Nose has the following information now that your baby is starting to roll. 

Give baby extra tummy time to play when awake and supervised as this helps baby to develop stronger neck and upper body muscles which in turn enables them to roll back over. 

Make sure that baby is on a firm and well-fitting mattress that is flat (not tilted or elevated).

Make sure that baby’s face and head remains uncovered (do not use lambswool, doonas, pillows, cot bumpers or soft toys)

As babies grow and develop they become very active and learn to roll around the cot.
At this time, continue to put them on the back at the start of sleep time, but let them find their own position of comfort.
By this stage it is not necessary to wake during the night to turn baby over to the back position

Do not use any devices designed to keep baby in a particular sleep position.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over 

ACECQA also provides this information:

Babies should be placed on their back to sleep when first being settled. Once a baby has been observed to repeatedly roll from back to front and back again on their own, they can be left to find their own preferred sleep or rest position (this is usually around 5–6 months of age). Babies aged younger than 5–6 months, and who have not been observed to repeatedly roll from back to front and back again on their own, should be re-positioned onto their back when they roll onto their front or side.
https://www.acecqa.gov.au/resources/supporting-materials/infosheet/safe-sleep-and-rest-practices