Karoki placed second at the 2015 IAAF World Cross Country Championships behind countryman Geoffrey Kipsang after leading for much of the race. He represented Kenya in the 10,000 m at the 2015 World Championships in Athletics and narrowly missed out on a medal in fourth place. Medals came at the 2016 IAAF World Half Marathon Championships, where he was runner-up to compatriot Geoffrey Kipsang Kamworor and shared in the team title.