[{users_ids:["122djdj-sdsddsl-3232323","2332333-443rdds-sdadads"],users_roles:{"122djdj-sdsddsl-3232323":"admin","2332333-443rdds-sdadads":"moderator"},users_names:{"122djdj-sdsddsl-3232323":"John Smith","2332333-443rdds-sdadads":"Paul Newman"}}]

db.collection.aggregate([{$addFields:{user_roles_arr:{$objectToArray:"$users_roles"},user_names_arr:{$objectToArray:"$users_names"},}},{$addFields:{admin:{$arrayElemAt:[{$filter:{input:"$user_roles_arr",cond:{$eq:["$$this.v","admin"]}}},0]}}},{$addFields:{adminId:"$admin.k",adminName:{$let:{vars:{adm:{$arrayElemAt:[{$filter:{input:"$user_names_arr",cond:{$eq:["$admin.k","$$this.k"]}}},0]}},in:"$$adm.v"}}}},{$project:{user_roles_arr:0,user_names_arr:0,admin:0}}])