Welcome TonyMac. We have used Correos previously when we walked the Camino del Norte in 2018, they are very good.
Hopefully if we can walk next year we will be using them again. Because of this we have just recently emailed them to ask a number of questions regarding our 2022 plans. We also asked the question you are asking.
The response was that you will need to meet with a Correos person at a bus stop very near the Albergue, between 8.00hrs and 8.30hrs, and give them your bags.
Our daughter used this service when she walked the Frances in 2019 and did exactly what Correos said to do re baggage collection and it worked perfectly.
We had an email reply to our enquiries within 24 hrs, they are very efficient. We also emailed them in English and they replied in English.
When we walked the Norte we had to contact them a couple of times by phone and there was always someone who was able to speak English.
We would suggest you arrange the pick up in Roncesvalles with them by email or phone the day before you require the pickup.
Their contact email address is on their website.
Hope this has helped.
Buen Camino.