The present methods, compositions and systems are concerned with biomolecule 130 detection, identification and/or quantification by rolling circle amplification (RCA) and Raman detection. In particular embodiments of the invention, the RCA is exponential RCA or linear RCA. In some embodiments of the invention, the Raman detection is SERS or SERRS. The circular DNA template 150, 210, 310 to be amplified may comprise one or more polythymidine 320 residues, resulting in amplification products 170, 230, 250, 330, 410 containing multiple polyadenylate 340, 420 residues. The polyadenylates 340, 420 may be directly detected by Raman detection. Alternatively, one or more Raman labels may be incorporated into the amplification products 170, 230, 250, 330, 410 to facilitate Raman detection. Because of the amplification produced by LRCA or ERCA and the enhanced Raman signal produced by multiple polyadenylates 340, 420 and/or Raman labels, detection of single copy biomolecules 130 is feasible using the disclosed methods, compositions and/or systems.