The independent consultant, a pensions adviser to the first Blair government, became best known for fighting subsequent Labour administrations in defence of workers stripped of their pensions.
Her pro bono campaigning work was finally recognised in last month's birthday honours with the award of the CBE.
Pensions minister Steve Webb said: "In appointing a business champion for older workers I wanted a powerful voice; someone respected amongst the business community, with a track record of speaking up for consumer rights without fear or favour.
"Older workers have a huge amount to bring to any workforce and are a vast, untapped talent in the UK labour market. The business case is compelling and I am delighted that Ros will now be taking a lead in going out and making that case directly to the business community."
Dr Altmann said: "I am so pleased that the Government has shown it recognises the importance of encouraging people to stay in the labour market, rather than giving up before they need to.
"A big part of my role is to work with employers to understand the significant benefits of retaining and recruiting older workers."