"Gradual rollout" refers to a process of introducing or implementing something slowly and in stages over a period of time, rather than all at once. Full definition
The Sundance Institute continued its gradual rollout of participants for the 2016 Sundance Film Festival by revealing the New Frontier program. (awardscampaign.com)
On January 15, 2010 Toyota Motor Corporation (TMC) announced its plans to begin a gradual rollout of its newly developed «G Sports» (G's) sports conversion car series. (tune86.com)
Given the uncertain regulatory environment and the newness of the technology, it makes sense to do a gradual rollout. (digitaltrends.com)