“Rocketman” is a musical fantasy, of Elton John’s breakthrough years. Taron Egerton plays Elton with flamboyant style and exuberance. He also uses his own singing voice to take us down memory lane. The film gives us a rare look at Elton as a child of a loveless father played by (Steven Mackintosh) and a selfish Mother (Bryce Dallas Howard), with Jamie Bell as Bernie Taupin Elton’s song writing partner.