Final answer:
The EMR Full Access Role is essential for managing permissions and access to AWS resources within an EMR cluster.
Step-by-step explanation:
The IAM role essential for managing permissions and access to AWS resources within a cluster in Amazon EMR is the EMR Full Access Role.
This role allows the user to perform actions such as launching an EMR cluster, creating and terminating instances, and accessing S3 buckets.
Other options like EC2 Full Access Role, S3 Full Access Role, and Lambda Full Access Role are not specifically designed for managing permissions and access within an EMR cluster.