Rural Opportunities for Broadband in Underserved Settlements and Towns Act or the ROBUST Act This bill requires the Federal Communications Commission (FCC) to determine whether spectrum usage rights under covered licenses are unutilized or underutilized in rural areas. A covered license is an FCC-issued license for the use of electromagnetic spectrum (1) whereby a licensee may use such spectrum for the provision of broadband service, and (2) that includes a rural area in any part of its geographic scope. If the FCC determines that a licensee's spectrum usage rights are unutilized or underutilized in a rural area, it must recommend that the licensee lease the rights to other entities to provide broadband service in that area. The bill also establishes prioritization and eligibility requirements for funding provided under the Department of Agriculture's Broadband ReConnect Program, which furnishes loans and grants for the costs of infrastructure needed to provide broadband service in rural areas.