INDIANAPOLIS—Zach Edey and Trevion Williams swapped roles for No. 3 Purdue on Saturday. If anything, it made the Boilermakers even more dangerous. Edey came off the bench for the first time this season, posted a double-double in the first half, and his presence helped open up the Boilermakers’ 3-pointers in a 77–48 rout over Butler at the Crossroads Classic. ”We’ve got 10 guys that can start for us, but they want to finish more than anything,” coach Matt Painter said, explaining the move. “Zach has had some struggles starting the game. The way Trevion played [against] North Carolina State, that factor is the reason for the decision. Trevion’s ability to pass can maybe help a couple of those guys starting.” Jaden Ivey took advantage by making all six 3-point attempts and finishing with 22 points. Edey wound up with 14 points, 11 rebounds, and two blocks while Williams, a preseason …