In January 1933 the NSDAP (Nazi Party) took power and lost little time in switching to one-party government in Germany. All political parties (other than the Nazi Party) were now illegal, but the new Chancellor had, in opposition, been particularly vitriolic about the Communist Party. In February 1933 Roscher emigrated to Czechoslovakia. He returned to Germany and settled in Dresden in August 1933, resuming his (now illegal) party work, but in December 1933 was back in Prague, in a hospital, thanks to his failing health. Subsequently, probably in 1934, the party sent him to Kharkiv (at that time in the Soviet Union) where he underwent a lengthy convalescence and also worked as an instructor for The Party. With the outbreak of the Spanish Civil War, in 1936, he joined the International Brigades. In Spain he fought in the Edgar André Bataillon. However, he was badly wounded in fighting outside Madrid in November 1936 after which he moved to Paris which was where the exiled German Communist Party had set up its headquarters. In April 1939 he was taken to the Soviet Union where he was accommodated in a rest home for wounded fighters from the Spanish Civil War, set up at Peredelkino, a dacha complex just outside Moscow. It was here that he would die in August 1940.