The sroB RNA is a non-coding RNA

Non-coding RNA

A non-coding RNA is a functional RNA molecule that is not translated into a protein. Less-frequently used synonyms are non-protein-coding RNA , non-messenger RNA and functional RNA . The term small RNA is often used for short bacterial ncRNAs...

 gene of 90 nucleotides in length. sroB is found in several Enterobacterial species but its function is unknown.
SroB is found in the intergenic region on the opposite strand to the ybaK and ybaP genes. SroB is expressed in stationary phase.
Experiments have shown that SroB is a Hfq binding sRNA

Hfq binding sRNA

A Hfq binding sRNA is an sRNA that binds the bacterial RNA binding protein called Hfq. A number of bacterial small RNAs which have been shown to bind to Hfq have been characterised ....

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Further evidence has shown that SroB negatively regulates the outer membrane protein YbfM by sequestering the ribosome binding site of ybfM mRNA by an antisense interaction.
Furthermore, SroB itself appears to be the target of a non-coding transcript from the chBC intergenic region.