He started his career in the theatre in the 1970s as an actor in small companies and experimental theatre. With the A.T.E.S. group he played lead roles in a variety of titles, the most important of which were between 1971 and 1975, -under te joint direction of Rafael Ramos and Roberto P. Gallegos- "Tiempo del 98", by Antonio Castro; Oratorio, by Jimenez Romero; "Guadaia al resucitado", by Gil Novales, in 1972; and "Ejercicios en la noche", by Juan Antonio Castro, in 1974. He also participated in "Un español del 27", on texts by Lorca diretced by R. Ramos and "Los opositores", by Mediero directed by R. P. Gallegos. In "Nenufares", by A. Canales, e¡in 1972; and the 1973 spectacle: "Cenas medievales", based on texts by Miguel de Cervantes, Lope de Rueda, Quevedo; directed by Alicia Canales.

Soon, in 1976, he finished this period devoted exclusively to acting and directs his first and one of his most award-winning plays: "Espectaculo Number One", followed by "El retablillo de Don Cristobal" by Garcia Lorca.

Shortly afterwards, he founded Caroca, the first professional theatre company in Cantabria, a milestone in the theatrical panorama of the region at that time. For more than ten years as director, and without giving up acting, he staged up to 10 plays that were being premiered around Europe at that time by authors such as Wittlinger, Gentile, Toller, Fo y Rame. Among some of the plays directed for Caroca in those times we can highlight "La pancarta", by Jorge Diaz in 1977; "Conoce Vd. la via lactea?", by Karl Wittlinger; and "Mambru se va a la luna", both in 1978.

The 80s represented intense theatrical activity for Roman Calleja in heterogeneous areas: Drama Studies added to the work with the company and individually in plays linked to poets, writers, and artists such as Jisquio or Cuevano. He continued his prodigious work as a director with titles such as "Tripode'r", by Isaac M. Cuende, in 1980; the plays by Guillermo Gentile: "Un bombon, un bombin y un baston", in 1982; "Las cucarachas", 1985; and, "Tira de la cadena", staged in 1986. More followed: that year "Pim-piribon-pim-pim", by Isaac Cuende; "Hinkemann", by Ernest Toller in 1987, with the Dante company and what was a premiere in Spain: "Un dia cualquiera", by Dario Fo and Franca Rame, starring Anabel Alonso in 1988.

As part of his mission to bring Theatre to the academic world, Roman Calleja gave classes at the Education Sciences Institution of the University of Cantabria, and at the Santa Clara Sixth Form Secondary School. He taught theatre as therapy, collaborating with psychiatrist Miguel Lopez Ors, at the AISNA (Mental Health Theatre Workshop).

Graduating from the Escuela Superior de Arte Dramatico, Sevilla in 1987 he took on a new appetizing challenge and founded with a small group of professionals the School of Performing Arts of Cantabria in 1988,of which he has been director and interpretation teacher ever since. Highlighted among the many plays staged were the tragic trilogy of Federico Garcia Lorca: "Yerma" (1993, 1999), "La casa de Bernarda Alba" (1997) and "Bodas de sangre" (1998).

In 1991 Roman Calleja was named Coordinador General Coordinator of the del Palacio de Festivales de Cantabria opened this year. Under his management the Drama School was installed in this new and spectacular stable location, as an active part of the production unit of dramatic arts housed in the centre.

Programming and teaching dominated the great part of his work during the following period but the stage was never far away from this man of the theatre and e directs "Caleidoscopio", based on texts Garcia Lorca, with the group Miriñaque Teatro, "Byzantium", a liturgical play for the Kontakion Choir (1996), and for the Cluj Philharmonic Choir(2004); and in 2003, "Hay que deshacer la casa" by Sebastian Junyet.

The start of the new century represented an important turning point in his career as a director, taking on projects outside Cantabria, in 2002 he directed the Spanish premiere of "Copenhagen" by Michael Frayn with Fernando Delgado, Sonsoles Benedicto and Juan Gea, a Fila Siete and Armonia production. He followed this in 2007, "Llama un Inspector" (An Inspector Calls) by J.B. Priestley, with Jose Luis Pellicena, Francisco Valladares, Concha Cuetos, Lola Manzanares, Ivan Gisbert, and Guillermo Muñoz, produced by Juanjo Seoane; a production that ran until June 2009.

For a director who goes out to meet creation and is not afraid to take risks, opera offers a different focus in stage work. With this in mind in December 2007 he used the stage of the Opera Theatre of Brasov, Rumania to show a pre-premiere of "The House of Bernarda Alba" an opera with text by Garcia Lorca and music by Miguel Ortega.The official premiere took place in two International Festivals ,Santander and Perelada in August 2009,with Raquel Pierotti, Monserrat Marti, Marina Rodriguez Cusi, Beatriz Lanza, Marina Pardo among others.

In line with the quest for distinctive theatrical expression, Roman Calleja undertook the direction of "La Voix Humaine", with music Poulenc and text by Cocteau, musical direction by Francesco Maria Colombo, and performed by soprano Raffaella Angelleti, produced by the Opera de Tenerife Festival of Opera in November 2009.

His latest production has been an adaptation and staging of "Romeo and Juliet" by W.Shakespeare with the opening and subsequent performances for the school campaign in the Palacio de Festivales de Cantabria, in 2011.