The process that gives rise to the rhombomere. This process pertains to the initial formation of a structure from unspecified parts. Rhombomeres are transverse segments of the developing rhombencephalon. Rhombomeres are lineage restricted, express different genes from one another, and adopt different developmental fates. [ GOC:cls http://openisbn.com/search.php?q=0838580343&isbn=1/ GOC:jid GOC:dgh http://purl.obolibrary.org/obo/go/references/0000021 GOC:dph ]