Transports riboflavin into the cell. Can also transport FMN and FAD. Required for normal nodule development during colonization of pea plant roots. Negatively regulated by riboflavin, probably via an FMN riboswitch. Belongs to the drug/metabolite transporter (DMT) superfamily. 10 TMS drug/metabolite exporter (DME) (TC 2.A.7.3) family.