[4] He returned to Georgia Tech to earn Master of Physics degree the following year, graduating as a presidential scholar summa cum laude in 2002.

[4] In 2002 Roper was selected as a Rhodes Scholar, and began study at University College, Oxford for a Doctoral program in mathematics with a focus on String Theory and quantum mechanics.

[9] From January 2006 to May 2012, Roper joined as technical staff at the MIT Lincoln Lab in Bedford, Massachusetts, attached to the Missile Defense Agency.

When he was discovered and hired by Secretary of Defense Ash Carter, the program he was slated to lead was conceived as a way to extend the shelf-life of technology and systems which were falling behind the cutting edge, but Roper saw the potential of the material available to the office, and led the program in a different direction, creating a skunkworks for future warfare which innovated radically new ideas from disused and surplus systems.

He led the office to tackle new and diverse concepts including hypervelocity artillery,[12] multi-purpose missiles, autonomous fast-boats, smartphone-navigating weapons, big-data-enabled sensing, 3D-printed systems,[12] standoff arsenal planes, fighter avatars, missile defeating hypervelocity rifles,[13] and fighter-dispersed swarming micro-drones[14] which formed the world's then-largest swarm of 103 systems.

[15]One notable failure of the program under Roper's leadership came when employees at Google demanded the company abandon the Algorithmic Warfare Cross-Function Team working on artificial intelligence solutions to information ingestion issues, better known as Project Maven because of objections to the militarization of technology.

[27]Roper has attempted to turn the failures and delays of the long-beleaguered KC-46 Pegasus aerial refueling tanker project into an advantage by weaving fully autonomous operation capabilities into its redesign.

[28] He prioritized development of more effective multi-domain operation tools like Joint All Domain Command and Control (JADC2) and replacing JSTARS with the Advanced Battle Management System.

[31] Since the creation of the United States Space Force in December 2019, Roper has assumed a role in two highly classified programs within the service to build so-called e-satellites, "a Toyota-like satellite"[32] designed be a radically simplified, reliable, hard-wearing deployable craft eschewing traditional requirements like cleanrooms and expensive shielding, designed and engineered entirely within a digital environment before being produced in volume at low cost.

In a Zoom conference with reporters, he expressed his reservations at times with administration policy, but argued he was driven to continue by his deep concerns about a continued lack of awareness of China's military capabilities throughout the Pentagon saying "I don't think there is true cognizance and realization that we can lose — and that on paper, we're likely to lose" "The scale factors are against us in terms of GDP and population and STEM talent, every single factor is against.

[37] Following its publication, Roper told the U.S.-China Economic and Security Review Commission that he views competition with China as "one of the seminal challenges that we’re going to face in this century.