The translation by Old Possum is good. I'll add a bit more. I have some familiarity with these old Swedish ballads. That's not to say I understand every word of this at first sight.

One possible reason for the vår rather than min in the second omkväde line could be that it rhymes better with rosengård. Rhymes in omkväde lines are hardly common, but this does seem to be a very well-rhyming version of the ballad, so maybe. The other possible explanation has to do with her also being the mother of the dead brother: there is a plural again: oss in the final omkväde line (never expect us), and if that has something to do with the song (they don’t always), it could be referring to the son and his dead brother ... so perhaps that is also true of vår.

Here are the extra verses. As you can see, I don’t get all of them:

3 Kan iagh gott aff digh spöria:
Sonen i Roosengård:
Nu först det icke börias
Käre Moder wår

3. Can I ask you something, son in the rosegarden.
[[I think this means something like: don’t start that now]], dear mother of ours

4 Annat iagh ey tänker:
Sohnen i Roosengårdh,
dett werlden migh ihnskänker,
Käre moder wår

4. I don't plan on doing anything else (lit. I don’t think anything else), son in the rosegarden.
Whatever the world brings me, dear mother of ours.

5 Dageligh du dygdh öfwa:
Sohnen i Rosengårdh:
effter som dee migh pröfwa:
Käre moder wår

5. Every day you do good deeds, son in the rosegarden.
Because they test/challenge me, dear mother of ours.


10 Aldrigh du det förgäter,
Sohnen i Roosengårdh:
Jagh slipper fulle släter:
Käre Moder wår

10. You will never forget it, son in the rosegarden.
I will avoid ... [[?]], dear mother of ours.

14 Rundeligh kan du bööta:
Sohnen i Roosengård.
Jagh tohl ey dee migh hööta
Kära moder wår

14. You will pay in full, son in the rosegarden.
I can’t stand that they [you??] threaten me, dear mother of ours.

15 Zeel må du nähr migh wara:
Sohnen i Rosengård
Jagh blijhr ey vthan fahra.
Kära moder wår

15. [zeel??] You should be [zeel??] near me, son in the rosegarden.
[lit. I will not be not in danger], dear mother of ours.


17 Jagh hahr digh ähmat trösta:
Sohnen i Rosengård
Det är ey till det bästa:
Kära moder wåhr

17. I had thought I would comfort you, son in the rosegarden.
That would not be for the best, dear mother of ours.


19 Så will du hedan reesa:
Sohnen i Roosengård
Ja, dijt iagh rååkar lijsa
Käre moder wåhr

19. So you want to travel away from here, son in the rosegarden?
Yes, to wherever I happen to [?], dear mother of ours.


21 Så sägh migh då ditt Näste:
Sohnen i Roosengård.
Ey det på första Qwisten.
Ka ra Moder wår

21. So tell me then where your nest will be [lit. so tell me then your nest], son in the rosegarden?
Not on the first branch, dear mother of ours.


22 Då, huadh mehnar din fader:
Sohnen i Roosengård
på den är iagh ey gladher:
Kära moder wår

22. Then what will your father think, son in the rosegarden?
I am not happy about that, dear mother of ours.


23 Han will digh ighen tagha,
Sohnen i Rosengård
Jagh skall wäl annars lagha,
Kära Moder wår

23. He will take you back, son in the rosegarden.
I suppose I will have it otherwise, dear mother of ours.


24 Din fader digh wäll finner,
Sohnen i roosengård.
Nappast han migh hinner
Kära Moder wår

24. I suppose your father will find you, son in the rosegarden.
He will hardly find (reach) me, dear mother of ours.


25 Ähn Konungen i rijket:
Sohnen i Roosengård.
han finner wäl sihn lijke:
Käre Modher wåhr.

25. Even the king in his realm, son in the rosegarden.
I suppose he will find his [equal, or corpse, don’t know which], dear mother of ours.


26 Hwart hahr du ähmat lända
sohnen i Roosengård
Dijt werlden hahr ehn ända
Kära moder wår

26. Where do you think you will go, son in the rosegarden?
To where the world has an end, dear mother of ours.