Besides the Designated Players, various forms of General/Targeted Allocation money, and salary rules (conveneniently explained for you here), there is one other major roster restriction Major League Soccer teams face: they are only allowed to have eight international players on their roster. International slots can be traded from team to team, but Minnesota United has not been involved in any deals, so they've got the default eight.
As of today, the Loons look to have used up all eight of their slots (but maybe not—see below). The eight players on the roster are as follows (in no particular order):
Johan Venegas, Costa Rica
Francisco Calvo, Costa Rica
Mohammed Saeid, Sweden
Vadim Demidov, Norway
Rasmus Schüller, Finland
Jermaine Taylor, Jamaica (see update)
Bernardo Añor, Venezuela*
*There is some speculation that Ibson and Añor may be able to qualify as domestic players.
It should be noted that the roster is not finalized, as more players can be brought in along with additional international slots, and some players may obtain a green-card or other forms of papers to qualify as a domestic player. For more information on the eight players listed above, click on their name.
UPDATE: Our fantasic commenters pointed out that Jermaine Taylor has been in MLS long enough to count as a domestic player. Thank you to those who fact-checked this article!