Root made a fluent 73 to lay the platform for England's imposing total of 328 for six and he took three wickets with his part-time off-spinners to help the hosts win the series 2-0.
Eoin Morgan scored 76 and shared a third-wicket partnership of 140 with Root before Jonny Bairstow's sparkling unbeaten 72 off 44 deliveries gave the England innings a late boost.
Ireland captain William Porterfield struck a battling 82 but his team lost wickets at regular intervals and they were dismissed for 243 in the 47th over.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
England play South Africa in a three-match one-day series before hosting the Champions Trophy next month.
(Reporting by Ed Osmond, editing by Pritha Sarkar)
