The company, which has a turnover of £3m, has also recruited Perth Racecourse sales manager Amanda Kirk, who joins as business development manager.
McIntosh, who joined Roselle in 2010, will report to chief executive Joanna Daley, while Kirk will report to McIntosh.
Roselle has offices in Edinburgh and Aberdeen. In 2011 it experienced a 30% growth in turnover and planned and organised 76 events across six countries. It works with corporate clients on events including conferences, incentives and product launches.