Who is responsible

Suppose, you are working in a software development project as a software architect. You are still waiting for the requirements to be available in sufficient quality and quantity and priorization. Even after months almost nothing happens. Sure, the problem is caused by requirements engineering. But what is your responsibility as an architect? Your responsibility is to communicate and escalate which requires courage. For example, you could tell the stakeholders what implications the current situation might have - for example, you cannot start with architecture design which means development cannot start with implementation etc. You should never fall into the "this is not my job" trap. After all, software architects need to drive the project. Sometimes, it might be even possible to take responsibility for requirements as an architect but this should be the exception not the rule.
Similar issue for test & quality: if test coverage is only limited, bugs are seldomly found during testing, or tests themselves are faulty, then you could finger point to testers and developers. However, it is your job as an architect to deal with quality. Don't try to escape your responsibility in this area. Test First Design makes it very clear that testing requires the different roles to cooperate.
What about business aspects? I know, you got this product manager who is in charge of all business aspects. But software architects are responsible in helping develop the technology roadmap, identifying patents, estimating the business implication of architecture decisions. Even more, architects must base every architectural decision on requirements and business needs.
Hmmh, what about project management? Of course, an architect should not be forced to also act as a project manager. These two rules are very difficult to live at the same time in the same project. But what if project management needs to estimate costs and resources? Here the software architect needs to provide support. What skills do developers need? How many developers and how much time are necessary to develop subsystem A.
I don't claim that architects shuld be jack of all trades but masters of none. Their main focus should be on software architecture. However, they cannot ignore what is happening on the boundaries between software architecture and the rest of the project. They should feel responsible for project success.