Come on ...
If there was no Roswell, where’d we get the idears for them fancy lazers, night vision goggles and ah-lou-mini-um foil? LOL!
Actually, John Titor visited them and introduced a number of technologies, but time travel was too much for the sensitivities of the general public, so they came up with “Roswell”. Corso fell for the classified cover story of alien visitation, but it was really a lone time traveller... LOL!!
Nicola Tesla, himselft either an alien, a time traveler or someone in touch with them, described all of them fancy thingies over 100 years ago.
Seriously, look up some of the things he did invent (not to mention the things he allegedly invented that have been "suppressed") such as a radio control torpedo (demonstrated to the public in Madison Square Garden in 1898!) or a little thing called radio (as we know it today, Tesla's patent was confirmed by the Supreme Court in 1943 after his death).