The Lost Hotel is located off of Route 15 just before the exit to Dendemille Town. Enter the ruins and go down the steps to find it. Inside, head south and take the second left, then follow the hallway west and turn north. The man here refuses to let you go any further because you don't have enough "style." Unlike the Boutique Couture, "style" in this case means roller skate tricks. Once you've received the roller skates and unlocked the northern half of Lumiose City, you can learn roller skater tricks in the following locations:
Trick #1: Backflip - By a tree just outside of the Hotel Richissime on North Boulevard.
Trick #2: Parallel Swizzle - Inside an office building on the western end of South Boulevard.
Trick #3: Running Start - By the monument in Vert Plaza.
Trick #4: 360 - Inside Cafe Rouleu on Estival Avenue.
With all four tricks learned, return to the man in Lost Hotel and he will let you through to see the Boss. He will teach you the game's fifth and final roller skate trick - the Cosmic Flip.