”Scream your heeeaaaaart ouuuuuut!” is such a perfect kicker for a pop-emo chorus, it should make ”Rooftops” — the catchy single from this Welsh act’s third CD Liberation Transmission — an instant classic. But like everything about this modern-rock band Lostprophets, it feels too studied to generate lasting emotion. The mix of pop-punk dynamics, classic-rock riffage, and hair-metal flourishes is well executed, and the lyrics channel teen angst with adequate drama. Around the world, 15-year-olds will fall for this band. Then they will turn 16 and move on.