ROI = Average Benefit Over Three Years / Initial Cost

The two most important factors to first look when assessing ROI potential are:

1. Breadth - How many people will be helped? If it saves a miniscule amount of time, but is used by everyone in your organization, it might be worth it.
2. Repeatability - How often will people use the application? Obviously you might see a return much sooner by automating daily tasks, rather than tasks that are performed annually.

Other factors you want to consider, are the potential to re-use the gained information in other areas, the increased collaboration to reduce more costly communication, and the cost of the task which is going to be affected.