Roundup was the codename for allied plans to invade northwest Europe in 1943. Eisenhower formulated this plan, along with plan Sledgehammer in 1941, before the U.S. had even joined the War. (Sledgehammer called for invading Europe in 1942, and was shelved in April of that year, when the plans were formally presented).
If the Russians had been weakened by the end of '42 such the the Germans could oppose this strongly, plan Torch (the invasion of North Africa) was to be used instead. Sub and shipping problems made it impossible anyway. In the fullness of time, Torch was implemented in 1942, then the invasion of Sicily and the Italian mainland occupied 1943.
At their November-December 1943 meeting in Tehran, Churchill and Roosevelt set May 1944 as the final date for operation Roundup. Thus it became the Normandy invasion.