These day most RPs are groomed as RPs in the minors, not failed starters who are converted in the majors.
Some will start their first few years in the minors, both to buildup arm strength and to give them enough innings to work on their stuff in game conditions.
But if you look at the Phillies RPs, the only ones who were slotted as SPs who became RPs are Madson, Morgan, Bastardo and Savary.
Arano, converted at 21 in Clearwater
Neris, always a RP
Ramos, always a RP
Rios, swing starter until he hit Reading at 23
Davis, started 11 games at Lakewood, then strictly a RP at Clearwater at 23
DeFratus, converted to RP at 21 at Lakewood
Giles, started 6 games at Lakewood at 21, then strictly a RP
Diekman, starter first two years in the system, then a RP at 22
Stutes, starter at Reading at 22, then converted to RP