Alexej Rosík studied at the conservatories in Žilina and Prague, at the Academy of Performing Arts in Prague, Sibelius Academy in Helsinki, Hochschule für Musik und Theater in Hannover and at Universität für Musik und darstellende Kunst in Vienna. He has successfully performed at concerts in England, Italy, the Netherlands, Germany, Finland, Norway, Japan and Thailand. He performed at Walt Disney Hall in Los Angeles with the Sibelius Academy Symphony Orchestra.
As a soloist he has worked with the Slovak Philharmonic, the Bohuslav Martinů Philmarmonic Orchestra, the National Chamber Orchestra in Žilina, with the Bohdan Warchal Slovak Chamber Orchestra and the State Opera in Banská Bystrica, Slovakia. He was accorded the role of concertmaster in Aldeburgh, England, with the Britten-Pears Festival Orchestra.
He has served as a concertmaster at the National Theatre in Prague (since 2011), the Prague Chamber Orchestra (2013–2015), the Czech National Symphony Orchestra (since 2013). He has cooperated with the likes of Carl Davis, Esa-Pekka Salonen, Marcello Rota, Ennio Morricone, Andrea Bocelli, James Newton Howard etc.