There are two rare breeds of pitcher: The relief pitcher (RP) with starting pitcher (SP) eligibility, and the SP with RP eligibility. These players can provide a ton of pitcher flexibility in daily H2H matchups. You can fill in those spots when your other pitchers have days off. Just adds to their values. Additionally, the SP with RP eligibility can be even more valuable when they are projected for 2 starts that week. You then reap the rewards for the additional Ks and possibly 2 Ws. Those are the ones I will be focusing on here. I will list all P with dual eligibility and the ones that have secured a spot in the rotation and those still battling for a spot. At this time I would disregard the other in standard leagues. They would be of value in leagues that have Holds as a stat.
On average for all leagues, Pitchers need to make 5 relief appearances to gain RP eligibility and will be eligible at SP after making 3 starts, either during last season or this season. Keep an eye on your league position eligibility page for the needed appearances to get qualified.