Show Me the Savings
Another strategy: Concentrate on cost avoidance rather than ROI. After all, revenue minus cost equals profit, and if you minimize cost, you are contributing to the bottom line in a tangible and important way.
There are some projects for which a large purchase makes sense if it will spare you from decreased quality of service and increased cost. For example, it's smart to upgrade to a new technology because the old one will cost far more over its useful life. One common example is the investment in Ethernet switches and NICs because of the high cost of maintaining aging token ring gear.
An example of a cost-avoidance strategy that might strike close to the hearts of the folks with the checkbooks is the purchase of software--for example, document imaging, or perhaps a data-conversion package--that lets a department avoid hiring temporary employees during a seasonal rush.
When you are looking at ways to save a department money, it pays to think about fixed costs versus variable costs, too. Fixed costs are those where unit volume doesn't matter--for example, a factory building or your Internet connection. Variable costs are those that increase as your unit volume goes up--software licenses and hourly labor, for instance. You're probably already pretty good at identifying ways to save money within IT--for example, switching to incident-based support where it makes sense. But as you start looking at the way departments work, think to yourself, "How could I save some money for these folks by applying IT to their problems?" Visit the departments. If you see users manually converting images to the format their database supports, clue them in to automated conversion tools.
You can strut your fly managerial accounting knowledge by showing that you know which situations require financial payoff analyses versus a more amorphous business benefit breakdown.