It's an international program with partners including CNES, ESA, Germany and Japan so difficult to cancel without picking up all their sunk costs. Plus the launch and mission support contract was signed with SpaceX back in 2022* for a Falcon Heavy. They would Zalsohave topic up all SpaceX costs for long-lead items already procured - and with launch planned next year that will be all of them.
Probably cheaper and easier to proceed than cancel.
*
https://www.nasa.gov/news-release/na...ace-telescope/
...."NASA has awarded a NASA Launch Services (NLS) II contract to Space Exploration Technologies Corporation (SpaceX) in Hawthorne, California, to provide launch service for the
Nancy Grace Roman Space Telescope mission. The Roman Space Telescope is the top-priority large space mission recommended by the 2010 Astronomy and Astrophysics Decadal Survey.NLS II is an indefinite-delivery/indefinite-quantity contract. The total cost for NASA to launch the Roman telescope is approximately $255 million, which includes the launch service and other mission related costs. The telescope’s mission currently is targeted to launch in October 2026, as specified in the contract, on a Falcon Heavy rocket from Launch Complex 39A at NASA’s Kennedy Space Center in Florida.....
NASA’s Launch Services Program at Kennedy is responsible for launch vehicle program management of the SpaceX launch service.".....