The Roman Space Telescope is based on an existing 2.4 m (7.9 ft) wide field of view primary mirror and will carry two scientific instruments.

The Coronagraphic Instrument (CGI) is a high-contrast, small field of view camera and spectrometer covering visible and near-infrared wavelengths using novel starlight-suppression technology.

Stated objectives[6] include a search for extra-solar planets using gravitational microlensing,[7] along with probing the chronology of the universe and growth of cosmic structure, with the end goal of measuring the effects of dark energy,[8] the consistency of general relativity, and the curvature of spacetime.

In 2012, another possibility emerged: NASA could use a second-hand National Reconnaissance Office (NRO) telescope made by Harris Corporation to accomplish a mission like the one planned for WFIRST.

L2 has disadvantages versus geosynchronous orbit in available data rate and propellant required, but advantages for improved observing constraints, better thermal stability, and more benign radiation environment.

[22] The science objectives of Roman aim to address cutting-edge questions in cosmology and exoplanet research, including: The telescope is to carry two instruments.

[29] On 29 September 2021, NASA announced that Roman had passed its Critical Design Review (CDR), and that with predicted impacts from COVID-19 disruptions, and with flight hardware fabrication completed by 2024 followed by mission integration, the launch date would be no later than May 2027.

[34] On 18 February 2016, NASA announced that Roman had formally become a project (as opposed to a study), meaning that the agency intends to carry out the mission as baselined;[9] at that time, the "AFTA" portion of the name was dropped, as only that approach is being pursued.

[38] NASA announced (Jan 2018) the reductions[clarification needed] taken in response to this recommendation, and that Roman would proceed to its mission design review in February 2018 and begin Phase B by April 2018.

[40] In February 2018, the Trump administration's proposed an FY2019 budget that would have delayed the funding of the Roman (then called WFIRST), citing higher priorities[clarification needed] within NASA and the increasing cost of this telescope.

[42][43] The American Astronomical Society expressed "grave concern" about the proposed defunding, and noted that the estimated lifecycle cost for Roman had not changed over the previous two years.

NASA announced the completion of the Preliminary Design Review (PDR) on 1 November 2019, but warned that though the mission remained on track for a 2025 launch date, shortfalls in the Senate's FY2020 budget proposal for Roman threatened to delay it further.

[54] In 2018, a contribution from Germany's Max Planck Institute for Astronomy was under consideration, namely the filter wheels for the star-blocking mask inside the coronagraph.

[58] In May 2018, NASA awarded a multi-year contract to Ball Aerospace to provide key components (the WFI Opto-Mechanical Assembly) for the Wide-Field Instrument on Roman.