Before Yale, he was on the economics faculty at the University of California, Davis, and before entering academia Roemer worked for several years as a labor organizer.
He became intensely involved in the anti-Vietnam-War movement, transferred to the doctoral program in economics, and was suspended by the university for his political activities.
He was past president of the Society for Social Choice and Welfare and served on the editorial boards of many journals in economics, political science, and philosophy.
Roemer has contributed mainly to six areas: Marxian economics, distributive justice, political competition, equity and climate change, and the theory of cooperation.
Roemer's early work was an attempt to state the main themes of Marxian economics using the tools of general equilibrium and game theory.
Roemer's program was then to propose definitions of embodied labor time, for economies with more general production sets, which would preserve the CECP.
While writing A General Theory of Exploitation and Class (1982), Roemer met the philosopher G. A. Cohen and the political theorist Jon Elster: they and others had formed a group of like-minded Marxists, young social scientists and philosophers who saw their task as reconstructing Marxism on solid analytical foundations, using modern techniques.
He was strongly influenced by Cohen, whose work Karl Marx's Theory of History: A Defence (1978) was to become the gold standard of analytical Marxism.
In Roemer, Lee and Van der Straeten (2006), it was applied to analyze elections in four countries, where the two dimensions of policy were postulated to be taxes and immigration (or the race question).
In Roemer (2006), a dynamic model was studied, where the question posed is whether political competition over the long period would tend to produce more economic equality, through democratically chosen policies of educational finance.
In Llavador, Roemer, and Silvestre (2012) the authors propose how the bargaining problem between the global North and South can be resolved, over the allocation of rights to emit greenhouse gases.
In Roemer and Silvestre (1993), the authors proved the existence, for quite general economic environments, of an allocation they called the proportional solution (PS): an allocation of goods and labor which is Pareto efficient, and in which each receives goods whose value (at supporting efficiency prices) is proportional to the value of their expended labor.
In Roemer (2011), it is shown that, in a variety of games, Kantian equilibria deliver Pareto efficient allocations—they rectify the inefficiencies associated with Nash equilibrium.