Ripe Bartlett pears work best here as they are quite juicy and their silky flesh turns pleasantly soft during the roasting process. If you are considering using another type of pear, just make sure they are ripe and juicy. Both ripe Comice and Anjou pears could stand in for the Bartletts in a pinch. Apples will not soften nearly as much as pears during the roasting process so I don't recommend using them here in place of the pears.