Roche in July had flagged an expected slowdown in demand for the tests in the second half of the year, but management was more confident this time.
"(COVID-19) testing is likely to continue into the fourth quarter, and likely into next year. The question is the level of testing," said Thomas Schinecker, head of Roche's diagnostics business.
That would depend on several factors, including the pace of vaccination, Schinecker added on a media call.
Group sales in the three months to September rose 8% to 15.97 billion Swiss francs ($17.29 billion), the company said, as diagnostics division revenues jumped 18%.
Analysts on average were expecting sales of 15.48 billion francs, according to Jefferies.
"The quality of the beat is somewhat worse than we wished for - key growth drivers underperformed," Vontobel analysts said in a note, adding that the beat comes from Actemra, which profits from the pandemic, and a slower erosion of key oncology drugs.
Shares in the company were down 0.3% by 0848 GMT, compared to a near 1% rise in the wider European pharmaceuticals index .SXDP .
Roche, whose medicines RoActemra/Actemra and Ronapreve have been critical to COVID-19 treatment in several countries, said supply of biological ingredients for those drugs was improving after the situation had been tight.
There have also been signs of recovery in the pharmaceuticals unit since the summer, the company said, after the pandemic hurt sales.
A plethora of new launches, including an Alzheimer's treatment if approved by U.S. authorities, are expected to bolster future sales at Roche as it faces increasing competition for older drugs.
Final data from a study of its experimental COVID-19 antiviral pill, which Roche is working on with Atea AVIR.O , will be submitted to a peer-reviewed publication and the partners will continue to analyse data, the company said.
The pill had failed to help patients with mild and moderate COVID-19 in a small study of mostly low-risk patients, delivering a major setback to the firms.
($1 = 0.9238 Swiss francs)
(Reporting by Pushkala Aripaka in Bengaluru and Michael Shields in Zurich; Editing by John Revill and Jan Harvey)