For a review of the role of RNA in the origin of life, see this compilation of papers on the subject:
Gesteland, $R . F_{-}, T . R .$ Cech, and $J . F .$ Atkins (eds.). $2006 .$ The nature of modem $R N A$ streeests a prebiotic $R N A$ world. Cold Sprine Harbor Monograph Series $43 .$ Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.
And see this paper for an interesting computer model of what might happen once an RNA population manages to achieve self-replication:
Kuhn, C. $2005 .$ A computer-glimpse of the origin of life. Jourmal of Biological Physics $31: 571-585$