I read somewhere that Express Bourricot will pick you up from Orisson and drive you back to Sjpp for the night then back up to Orisson the next morning. Check them out maybe.
Yes, and this is an excellent option.
I've seen many many pilgrims ruin themselves on that first day from SJPP to Roncesvalles.
It can be grueling if a person is not in shape.
With my groups, we walk to Orisson the first day from SJPP.
Express Bourricot picks us up around 2 pm and delivers us back to SJPP where we spend our 2nd night.
Next morning, EB picks us up and delivers us back up at Orisson, where we have breakfast, then continue on to Roncesvalles.
It makes both stages easier and saves injuries.
Just to be clear, the first section up to Orisson is only 8-9 kilometers, but they are VERY STEEP for most people and it can take 2-4 hours to walk it.
The next day, it's not so much the climb that is dangerous, but the steep descent down into Roncesvalles when you are exhausted.
If it is raining, it is as slippery as snot and scary.
You definitely need walking sticks.
And then, the next day, the descent into Zubiri is also steep and slipper if it's raining.
If you've done the first stage in one day, your legs will be like rubber.
So, if you are in excellent shape, do it in one day.
However, if you have doubts, break it up into two days and don't break yourself.
There's no shame in being smart.
If you DO decide to do it in one day, this is my advice:
Start early
Walk slow - pace yourself
Take a break every hour or two where you stop, take off your shoes, rub your feet, and hydrate
Take food/snacks and eat every couple of hours
Don't be in a hurry - there are plenty of beds in Roncesvalles and I have never heard of any pilgrim being turned away there
My own experience on my very first Camino was that I made reservations at Orisson.
Then the hospitalero at SJPP told me, "Oh, don't stop at Orisson - just walk it all the way through!"
So I cancelled my reservation at Orisson.
I cried (literally) every step down that freaking hill into Roncesvalles and I said very bad things about that hospitalero for days.
That night, when I had to put my feet on the hard, round ladder step to get down from my bunk to use the toilet, I cried again, as my feet were so painful.
Those were the worst two days of my Camino and it took about a week to recover completely.
I never have done that again.
I always break it up into two days.
If you can't get a reservation at Orisson, it's easy to get a 2nd night in SJPP and use the taxi service.
That's my advice.