Anyone know any names that have both [name]German[/name] and Scandinavian roots?
There are lots:
That is behind the names list for [name]German[/name] names. Many of the names also have Scandinavian listed as an origin.
My personal favorites are [name]Andreas[/name], [name]Alexander[/name], [name]Felix[/name], [name]Jonas[/name], [name]Otto[/name], [name]Charlotte[/name] and [name]Sylvia[/name], but there are lots of other great names.
You can also look at Behind The Name’s list of Scandanavian names here: Scandinavian Names - Behind the Name
There are way too many for me to just compile a list, but I have seen lots of the names here listed as Scandanavian (Norwegian, Danish, Swedish, Finnish Icelandic & Norse) and also [name_m]German[/name_m]. A little history lesson for you: the reason why they share so many names is that a good portion of Scandanavian & [name_m]German[/name_m] names are Germanic in origin. The ancient Germanic people group inhabited land in both Germany and many Scandanavian countries and because the Germanic people all spoke the same language, you get lots of shared names. 
I would recommend checking out these lists: Scandi Familiars - British Baby Names and Scandi Particulars - British Baby Names.
If you look at ‘[name_m]German[/name_m] names’ (for example) on Behind the Name it shows you names that are in use in Germany, not necessarily names with Germanic roots. E.g. [name_m]Andreas[/name_m] and [name_m]Alexander[/name_m] have Greek roots, not Germanic, [name_m]Felix[/name_m] is Latin, [name_m]Jonas[/name_m] is Greek from Hebrew etc.
Scandinavia is [name_u]Sweden[/name_u], Norway and Denmark. The Nordic countries are [name_u]Sweden[/name_u], Norway, Denmark, Iceland and the Faroe Islands. Finland is completely different. The closest living language to Finnish is Estonian, it’s a whole other kettle of fish.
But yes, Scandinavians and Germans have shared ancestors, and they both speak Germanic languages. The group of people that spoke the original Germanic language split into [name_u]North[/name_u] Germanic, sometimes called the Nordic languages (Swedish, Norwegian, Danish, Icelandic and Faroese), [name_u]West[/name_u] Germanic (English, [name_m]German[/name_m], Dutch and a few others) and [name_f]East[/name_f] Germanic (now extinct). So there is a ton of overlap between the [name_u]West[/name_u] Germanic and [name_u]North[/name_u] Germanic languages. It doesn’t really make sense to say that the name [name_m]Harald[/name_m], for example, has “both [name_m]German[/name_m] and Scandinavian roots”. Rather it has Germanic roots, as do the Scandinavian languages and modern [name_m]German[/name_m].
So some boy’s names with Germanic roots that are still used in both Germany and Scandinavia:
[name_m]Albert[/name_m]
[name_m]Alfred[/name_m]
[name_m]Bernhard[/name_m]
Björn
[name_m]Carl[/name_m] / [name_m]Karl[/name_m]
[name_m]Erik[/name_m]
[name_m]Gustav[/name_m] / Gustaf
[name_m]Harald[/name_m]
[name_f]Helge[/name_f]
[name_m]Henrik[/name_m]
Ingolf
[name_m]Knut[/name_m]
[name_m]Konrad[/name_m]
[name_m]Lars[/name_m]
[name_m]Lennart[/name_m]
[name_m]Olaf[/name_m]
[name_m]Otto[/name_m]
[name_m]Ralf[/name_m] / [name_m]Ralph[/name_m]
[name_m]Robert[/name_m]
[name_m]Rolf[/name_m]
[name_m]Rudolf[/name_m]
[name_m]Sigmund[/name_m]
[name_m]Sven[/name_m]
[name_m]Thorsten[/name_m] / [name_m]Torsten[/name_m]
[name_m]Waldemar[/name_m] / Valdemar
[name_m]Walter[/name_m] / Valter
[name_m]Werner[/name_m] / Verner
I was going to suggest behindthename.com as well… (now I feel like a broken record).
[name_u]Sweden[/name_u], Norway, Germany, and Denmark are all Germanic cultures and have Germanic word roots.
Look up Ancient Germanic or Germanic Mythology names and you’ll probably find names that have variants that are used in both cultures.
Also if you have a name you love that isn’t Scandinavian or [name_m]German[/name_m] you can also look that up on BTN and look at the list of variants at the bottom and see if they have variants that fit your demands that you like…