The enzyme which transcripts a double stranded DNA copy from a single stranded RNA template molecule is:
Reverse transcriptase transcripts a double stranded DNA copy from a single stranded RNA template. This enzyme is programmed to use a single-stranded RNA template, and to synthesize a complementary DNA (cDNA) strand. Ref: Measuring Gene Expression, Matthew B. Avison, 2007, Page 135
DNA polymerase
RNA polymerase
Reverse transcriptase
Phosphokinase