The leader of the Scottish Conservatives said Mr Johnson was focused on the UK Government’s response to the Covid pandemic which, along with travel restrictions, would prevent him coming to Scotland
Stressing the Holyrood election campaign was "very different" due to the virus, he said: "It’s not as simple and as easy or as straightforward.
"At the moment I don't believe the Prime Minister will be coming up given the circumstances we're dealing with and the fact that he continues to lead the UK Government's response to Covid-19, the vaccine rollout and getting us through this pandemic.
"But I'm in touch with the Prime Minister, he understands it's our campaign being led by me up here in Scotland."
Mr Ross said "things could still change and “the Prime Minister could pop up at the end of the campaign."
Mr Johnson has previously said "wild horses" would not be able to keep him away from the election campaign when he visited Scotland earlier this year at a time when coronavirus levels were higher and a “stay at home” order was in place.
Asked if Mr Johnson's absence would be better for his campaign, given his unpopularity in Scotland according to opinion polls, Mr Ross said: "I work closely with the Prime Minister.
"He knows the campaign we're running here in Scotland, and he's absolutely behind the Scottish Conservative efforts to stop an SNP majority and to get the focus of Scottish politics back on recovery and rebuilding after the pandemic."