In a few different video games I've encountered, cultures styled after Vikings had a building made of a longboat. The longboat had been flipped over to form the roof and rafters of the building. One example from a popular game is here.
Does this have roots in history or is this invented?
No. It wouldn't have made sense for a number of reasons.
The shape wasn't right. Longboats were thin and flat-bottomed, which means they'd trap smoke below and gather heavy snowfall on top. That's not great for living in and it's dangerous for the building. Merchant ships had deeper hulls which might provide a better roof once flipped, and they were also reasonably wide, but they were probably shorter than desired and less prestigious among elites. Either option would require extensive reworking.
The material wasn't right. The outer hulls would have been tarred with burnt pine resin, and in between all the planks, there was caulking made from wool and more tar. That would make for a very flammable roof for a dwelling with an open hearth. It would also drip tar on everybody and everything, making it difficult to keep clean, cook, weave, or preserve household goods. Even if the tar could be removed, there would still be iron nails dripping rust or more likely holes left from where the iron had been removed for recycling. And there may have been all sorts of barnacles and bacteria living on the outer hull, too, which might either yield a new ecosystem as part of a roof or decay into a reeking mass.
I think that supports the conclusion that (1) Viking-Age Scandinavians wouldn't want their roof to look like an inverted boat, and (2) they wouldn't have recycled boats or boat parts into their roofs. There may have been some limited recycling in Iceland and Greenland where wood was extremely scarce and almost entirely imported, but it seems like these settlers rapidly learned to make woodless buildings by using cut turf.
So what did Viking-Age buildings look like? Helena Hamerow has published a few easy-to-find books that touch on the subject, but to get a quick sense of things, I'd point you to the longhouses reconstructed at the Lejre Land of Legends. The roofs have a bowed shape, which admittedly looks a bit similar to a keel, but is not actually the same shape. Towns seem to have had timber-framed houses, which could plausibly have incorporated recycled wood from boats, but the roofs were entirely different. The reconstructions at Hedeby provide a decent example.