Santa Rosa de Copan sits on the CA-4 highway in western Honduras. Direct buses run from San Pedro Sula (about four hours), which is the main hub for connections to the rest of the country and has the nearest international airport. From Copan Ruinas the ride is roughly an hour. Buses to Gracias leave several times daily. If you are coming from Guatemala, cross at El Florido and connect through Copan Ruinas.
The old Santa Rosa de Copan Airport closed years ago and has not reopened, so flying in is not an option. The bus terminal sits on the edge of town; from there it is a short taxi or tuk-tuk ride to the centre.