Mateo Rosales, based in Valencia, Spain, specializes in medieval Spanish lineages and municipal archives from the Crown of Aragon. His work often focuses on reconstructing families from fragmented notarial records and early taxation lists. Rosales is known for his ability to interpret old Valencian and Catalan documents, which has earned him a reputation among researchers studying diaspora communities throughout Latin America. He regularly lectures on paleography and the evolution of Iberian naming systems.