If the project is really short 2-3 months, then ofcourse Software Architect has to do Technical Lead Role once he completes the design. He can setup Code Review tools like PMD ,etc for his project,review the Code done by developers w.r.t to the design that you made, help the developers in fixing the technical issues, if any, etc....
As Jonathan pointed out it depends on the Company's policy that you work. In Some company they will ask the Architect to move to the next project even.
If you want to know the complete Roles and responsibilities of an Architect, Please read the Book " J2EE Architects Handbook" which is very useful.