The same thing they should do anywhere else, and this has not changed since the days of building cathedrals from stone: 1. Design. 2. Supporting the implement

The same thing they should do anywhere else, and this has not changed since the days of building cathedrals from stone: 1. Design. 2. Supporting the implementation effort of the design. 3. Governance, i.e. making sure that what was designed is what is delivered. Of course there are many other tasks that a software architect in particular has to carry out, but in my day job I never stray too far from the three fundamentals above.