Dr. Roychoudhury is among the first few who initiated genomic research in India. As a cancer biologist, he contributed significantly to the molecular understanding of the genomic instabilities, and functional consequences of gain-of-function p53 mutations in human cancer. He has also contributed significantly to the area of cancer stem cells using the oral cancer model. He has developed a microarray-based gene expression signature that distinguishes the aggressive subset of early-stage oral cancer from the non-aggressive one. Currently, he is developing algorithms based on molecular classifications of ovarian and endometrial cancers for prognostic and therapeutic decisions.

He published more than 180 research papers and other articles. Dr. Roychoudhury has seven genomic data submissions, one patent, and one copyright to his credit. He supervised 24 PhD students. Dr. Roychoudhury is the Fellow of all three Science Academies of India. He was elected as President of the Indian Association for Cancer Research (2016-2019). He was awarded the J C Bose National Fellowship by the Department of Science and Technology, Govt. of India in 2017.