The link is dead. Here is the link to the timetable for the line Pamplona to Roncesvalles until 30 June 2021:
https://www.autocaresartieda.com/pdf/roncesvalles.pdf
General information about price, ticket purchase and duration:
https://www.autocaresartieda.com . Paste the text into
Google Translate if you need a translation into English. The website says that you cannot book by internet or phone and that you buy the ticket from the bus driver on the day of travel and just before the departure.
@lizlane, I remember your posts from earlier and I am pleased to read that you are now so close to realising them. Things are changing rapidly, and for the better, in terms of availability and ease of travel. At the moment, there is only this one bus connection from Pamplona to Roncesvalles once a day and none on Sundays and public holidays. There may be more connections per day as of July, and the international ALSA bus connection from Pamplona to SJPP may be reinstated by then, too.
If you plan your trip until Pamplona (plane, bus, or train from Madrid airport - travelling on Spanish long-distance busses is quite comfortable), perhaps with a first night in Pamplona, you will still be flexible on the day to decide whether to start in Roncesvalles or SJPP if you want to; SJPP to Roncesvalles and vice versa is well served by taxis, it's a 30-minutes, 18-miles trip. If you have the time, start your walk to Santiago leisurely, don't hurry or stress to reach the starting point. Bon voyage and Buen Camino!
PS: There are currently only two ALSA buses from Madrid airport to Pamplona on 8 June for example, but again, the frequency could increase by the time you arrive in Spain.