My baby is nearly 14 weeks old, has not started rolling & still has startle reflex, so I am currently putting her in an ergo pouch to sleep. Once she is rolling/startle reflex gone, do I simply put her arms out of the ergo? Or get rid of it all together? And then still no blankets in the cot, correct?

Red Nose does recommend you cease wrapping once baby is attempting to roll. The startle reflex would be reduced by now, but may also still be evident.
If you wrap your baby, consider baby’s stage of development. Leave arms free once the startle reflex disappears around 3 months. Most babies eventually resist being wrapped. Wrapping style should be appropriate for the baby’s developmental stage.

It is essential to discontinue wrapping as soon as baby starts showing signs that they can begin to roll, usually between 4-6 months of age but sometimes younger. Babies must not be wrapped if sharing a sleep surface with another person. Baby should not be wrapped while sleeping in a baby sleeping bag.
https://rednose.org.au/article/is-it-safe-to-wrap-swaddle-my-baby
Red Nose recommends to move baby to a cot & cease wrapping once baby is attempting 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

Blankets can be used as long as they are tucked in tightly & are not at risk of becoming loose & covering baby’s head & face.
Once baby is rolling, blankets are often not used, as baby tends to move out from under blanket or kick it of, where there is a risk of head & face being covered.
Parents often choose to use a sleeping bag, with appropriate fitting arm & neck hole (& no hood)
An extra layer of clothing can be added under the sleeping bag if necessary.