New deputy leader Stewart Hosie MP will oversee the manifesto.
Announcing the appointments, SNP leader and Scottish First Minister Nicola Sturgeon said the pair had "substantial records of electoral success".
The SNP says it could hold a balance of power at Westminster in what it sees as the increasing likelihood of a hung parliament.
Mr Robertson said that the more votes and seats the SNP wins next year, the "more the Westminster establishment will have to pay attention to what people in Scotland want".
He added: "We have more members than ever before to take our message to the people - with around one in every 50 adults in Scotland now in the SNP - and by working as a team at all levels I am confident but never complacent about our prospects."
The general election takes place on 7 May next year.
The SNP has appointed MP Angus Robertson to run its party's campaign for the 2015 Westminster election.