Final answer:
The success of the implementation and roll-out is most evidenced by the end users, such as customers or clients.
Step-by-step explanation:
The success of the implementation and roll-out is most evidenced by the end users. While expert analysis, technical staff, and professional evaluators play important roles in the evaluation process, the ultimate measure of success is how well the end users, such as customers or clients, are satisfied with the implemented system or program. Their feedback and experience are crucial in determining the effectiveness and overall success of the implementation.