It comes just three days after Lufthansa chiefs announced the introduction of daily flights between the west coast hub and the German city of Dusseldorf after deciding to ditch Edinburgh Airport.
Jet2 doesn't operate a winter service to the Italian or Spanish cities. However, that will change next year when the airline introduces twice weekly flights to both cities from March 28.
The airline's chief commercial officer Steve Heapy said: "Rome and Barcelona are two of our most popular destinations and so we want to ensure customers can visit at any time of year."
He added: "With our generous 22kg baggage allowance people can take their winter woollies or summer gear and really make the most of their trips."
Amanda McMillan, managing director at Glasgow Airport, welcomed the new year round services. She said: "It is great to hear that Scottish passengers can now go and see these beautiful cities whenever they want as it's nice to be able to escape the low temperatures here in Scotland from time to time."
Confirmation comes just 72 hours after the Evening Times revealed how German airline Lufthansa left airport officials in Edinburgh raging by announcing they are to operate daily flights between Glasgow and Dusseldorf.
It has decided to scrap a partial service between Scotland's capital and one of Germany's wealthiest cities after research showed most of the outbound passengers lived closer to Glasgow. German visitors also said they would prefer to jet direct to Scotland's biggest airport than Edinburgh.