Roche announced last November that it was planning to build a facility in Shire Park, Welwyn Garden City. This would replace the Swiss-owned firm's existing facilities in the town, which include research laboratories, manufacturing space and offices.
The company appointed consultant Green Island Partners last year to sell the existing site. Roche has been based in Welwyn Garden City since 1937.
The scheme will house 600 staff and include space for product development, sales and marketing and corporate developments.
Roche is planning to complete the project in 2005.
A Roche spokesperson declined to comment further. The spokesperson said: "It is going through an internal approval process. We don't feel it is appropriate to talk about it until that process is complete."