Yes. If you put slightly wider tires then you can do packed earth or even gravel without too much trouble. Even 25 or 28mm tires give a lot of advantage over 18 or 23mm wide tires.
I did Col du Parpaillon on 25's.
From my trip report:
The hostel owner had said Col du Parpaillon was closed because of ice in the unlit tunnel at the top but we decided to try anyway. It's only about 22 km to the top but the top 10 km is unpaved and steep in places.
It wouldn't be very technical on a mountain bike, but everything is more technical on a loaded road bike. We only had to walk twice -- once trying to sneak up on a groundhog like rodent, and once over water.
The scenery was gorgeous. The path up wound past wildflowers and waterfalls backed by dramatic views of the mountains. The climb itself was cool -- it was overcast most of the day, but occasionally a few rays of sun would peak through to play across the mountainsides, and we saw no one else on the ascent, except for two German bikers about 2 km from the top. There were no houses on the ascent except for 3 hikers' shacks.
The tunnel was closed at the top, and was completely unlit, but I had a battery powered headlamp, so we decided to walk it. The water was a few inches deep in places, and there was ice in places, but we slogged through to find the German motorcyclists waiting for us on the other side. I think they may have taken bets on us, because they waved and left as soon as we exited the tunnel, and we saw them waiting again at the chapel at the bottom where the paved road starts.
I put on my arm and leg warmers for padding in case I got thrown from the bike, and then started descending. The first 5 km was a white knuckled descent over rough gravelly road punctuated with ruts and rocks. I heard thunder on the way down, and so sped up a little but not too much since I saw a few patches of fresh rockfall.
Just be careful of ruts on descents -- the narrower the tire, the more easily a rut will swallow a tire and prevent you from turning. When ascending on narrow tires over gravel and uneven ground, gear down and pedal continuously so that you always have a low level of power to move your front wheel. When there are sandy patches, plan turns so that you can do as much of your turning on packed earth, keep turns over sand as shallow as possible, and if the sand is deep avoid turning altogether.