Involved in the biosynthesis of the riboflavin analog antibiotic roseoflavin (3,8-dimethylamino-riboflavin) (PubMed:27062037). Catalyzes the site-specific substitution of the C-8 methyl group of riboflavin-5'-phosphate (FMN) by an amino group to yield 8-amino-8-demethylriboflavin 5'-phosphate, via a combined oxidation, decarboxylation and transamination reaction (PubMed:27062037, PubMed:27331868, PubMed:27981706). The catalysis is initiated by an oxidation step in which the C-8 methyl group on the dimethylbenzene ring of FMN is converted to a formyl group to yield the 8-demethyl-8-formylriboflavin-5'-phosphate (OHC-RP) intermediate (PubMed:27062037). In the presence of thiamine, the formyl group is oxidized into a carboxyl group to yield the 8-demethyl-8-carboxyriboflavin-5'-phosphate (HO2C-RP) intermediate (PubMed:27062037). Finally, in the presence of L-glutamate as an amino donor, decarboxylation and aminotransfer occur, resulting in production of 8-demethyl-8-aminoriboflavin-5'-phosphate (PubMed:27062037). Addition of NAD (but not NADP) to the reaction increases the yield 1.7-fold (PubMed:27062037). The reaction also proceeds without the addition of any electron acceptor, and it is possible that molecular oxygen serves this role (PubMed:27062037). 3 A + FMN + H2O + L-glutamate + O2 = 2-oxoglutarate + 8-amino-8-demethylriboflavin 5'-phosphate + 3 AH2 + CO2 + H(+) Antibiotic biosynthesis. Homotetramer. Cells lacking this gene are unable to produce 8-demethyl-8-aminoriboflavin (AF). Belongs to the SsuE family.