The former Shield brethren Roman Reigns and Seth Rollins played a big role in the main event spotlight of WrestleMania 40. The two were opponents on the Night One headliner touted to be the Greatest Tag Team Match of all time.
Then on Night Two, Rollins got involved in Cody Rhodes' main event match with Roman Reigns for the WWE Championship where The Shield backstory also played a big part as Reigns lost the title to The American Nightmare.

Moving on, Roman Reigns will be in an expected hiatus from the WWE and he is not scheduled to make any appearance on TV in the foreseeable future. At present, he is being advertised to appear on the final SmackDown episode of SummerSlam.
It does indicate that The Tribal Chief should be back in time to be a part of WWE's Biggest Event of the Summer. But given WWE will fly to Saudi Arabia for their next big PLE outing in the final week of May, he could be needed on that show.
In the reports of a recent edition of Wrestling Observer Newsletter, Dave Meltzer shed light on the post-WrestleMania status of the former champion and dismissed any sort of retirement rumors before noting SummerSlam to be his next in-ring outing.
"He'd take some time off. Given his limited schedule, one wouldn't even expect him on a show again until the as yet unannounced next Saudi Arabia show (last word being on 5/25) and the 8/3 SummerSlam show in Cleveland."
As for Seth Rollins, he's banged up for a long time for the constant grueling schedule during his World Heavyweight Championship reign. His body necessarily needed a break and it started from WrestleMania 40 Night Two onward.
According to the Wrestling Observer Newsletter, Seth Rollins is expected to be on a hiatus for about 4 weeks. The current assumption is that WWE will re-insert him into the storylines within the next Saudi Arabia event set for May 25.