Nordicized Latins. Romans who ended up integrated with Scandinavians. That happened.
Case in point, VK346:
This Y DNA sample is from a grave dated to 900 CE in Sweden. That speaks for itself. J-L283 inside the last 3,000 years traces namely to Illyrians and Romans, both in Italy, Sicily and Sardinia, and on the Eastern Adriatic. J-Z1043 appears to have migrated farther throughout Europe with a Roman of Illyrian descent who was stationed on the border of the Italic Roman Empire with Germania, or the barbarian territories to the north/west of the Rhine. How did J-Z1043 get to Sweden? Think about it.
By the time you get to the "Viking Age" in Northwestern Europe, that man's descendants were integrated strongly enough into the Nordic milieu at the time to be sailing around looking for better opportunities to take advantage of along with the rest of the Scandinavians, and to be buried in a clear "Viking" context.
This is not the only line of J-L283 to be integrated into Scandinavia. There are others, albeit without pre-medieval samples so far. Examine the Denmark and Norway DNA projects at FamilyTreeDNA and you'll find plenty of instances.
Other examples of overlap:
Research conducted by the University of Oslo in Norway in the border area of Croatia and Bosnia-Herzegovina revealed the first Illyrian trading post. This area (Narona) is remarkably close to where the earliest J-Z1297 is found, Gudnja Cave, near Ston Croatia, near the Neretva Valley, all of which is ascribed to the territory of the Illyrian tribe Siculotae (from whom the name of Sicily is believed by some to derive) (https://www.apollon.uio.no/english/articles/2008/illyrer-english.html).
Eliza Dushku of Buffy the Vampire Slayer fame (never seen it but it's well liked by some), is half-Albanian, and half-Danish. She and her brother made an interesting documentary about the Republic of Albania, one of the more interesting statements that she and her brother point out (which appears to be independently verifiable) is that Denmark and Albania are two of the only, if not outright, countries that held more Jews at the end of WWII than at the beginning (https://www.youtube.com/watch?v=XLhztVvky3I).
4 of the top 5 countries with the tallest people in the world are Denmark, Norway, Montenegro and Serbia (in some reports Bosnia-Herzegovina is included as well), obviously Scandinavian and historically Illyrian territory respectively (https://worldpopulationreview.com/country-rankings/average-height-by-country).