As Scotland's last coal-fired power station, the Longannet facility is due to close on 31 March.
Scottish Power said the high cost of connecting to the electricity grid was to blame.
The Longannet Task Force, jointly chaired by both the government and Fife Council, was set up to support workers, businesses and communities impacted by the closure.
The Scottish Government said it is continuing to investigate "what is needed, what is already being provided and what more can be done to bring more investment to the area".
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In his letter to Cllr Ross, Mr Ewing said: "We are committed to supporting sustainable and inclusive economic growth across Scotland. Our continued investment in infrastructure, regeneration and business support is helping to support economic growth and safeguard jobs across Fife, Clackmannanshire, Falkirk and North Ayrshire.
"We are making substantial investments in health facilities, education facilities, and road and rail projects and it is that sort of commitment that helps build the wider resilience and opportunities in the economy. Communities across the area have benefited from our regeneration funds.
"In establishing the Task Force, we recognised the need to work together to respond to the impact of the closure of Longannet. Your letter seemed to take very little notice of the commitment I gave at our last meeting that the Scottish Government would work with all Task Force members to explore how to deliver initiatives that would support people, business and communities most affected by the early closure of Longannet.
"Those detailed discussions are essential to identifying what can be delivered, drawing on existing resources and activities and building on the wider investment in the area. As the co-chair of the Task Force, I look forward to your commitment to supporting that process positively to ensure it delivers the best outcomes for those affected by the closure."
(LM)
