Yes it is easy, the taxi will take 4 persons.
Mondays to Fridays ... Pamplona to Roncesvalles is €50
Sat/Sun and National holidays the fare is €62
Mondays to Fridays... Pamplona to S.J.PP is €80
Sat/Sun and National Holidays the fare is €100
Various Taxi numbers prefix 948 ... 232300 :351335: 221144: 221212.
Pamplona to Roncesvalles by road is 44kms
Pamplona to S.J

P by road is 80 kms
This information and prices are from about a year ago so they may have changed.