Rural Delivery of Online Care Services Reauthorization Act of 2020 or the R-DOCS Reauthorization Act of 2020 This bill reauthorizes through FY2025 and otherwise modifies grants for telehealth networks and telehealth resource centers that serve medically underserved populations. Among other changes, the bill (1) provides statutory authority for including substance-use disorder providers in the list of entities that may participate in telehealth networks, and (2) specifies a preference for applicants with a record of success in expanding telehealth in rural areas for telehealth resource services grants.