Final answer:
The technician has completed the troubleshooting step of implementing a solution by installing a new fuser roller unit in a laser printer to address a printing issue.
Step-by-step explanation:
When a technician records that a new fuser roller unit was installed in a laser printer to resolve a printing issue, they have completed the step of implementing a solution in the troubleshooting process. This step follows several others, such as identifying the problem, gathering data, and analyzing the issue. After implementing a solution, the technician would typically test to ensure that the problem has been resolved. Implementing a solution usually involves the application of a fix or change, which, in this case, is the replacing or installing of a new component, the fuser roller.