Nevermind, figured it out!  I'm sure there's other ways but here's what I ended up doing in case anyone else finds it useful:
Select Top 1000000 tblO365Group.DisplayName As [Group Name],
  tblO365User.DisplayName As [User],
  tblAssets.AssetName,
  tblAssets.Lastseen,
  tblAssets.AssetID
From tblO365Group
  Inner Join tblO365GroupMember On tblO365Group.GroupId =
    tblO365GroupMember.GroupId
  Inner Join tblO365User On tblO365GroupMember.UserId = tblO365User.UserId
  Inner Join tblADusers On tblO365User.UserPrincipalName = tblADusers.UPN
  Inner Join tblAssetUserRelations On tblADusers.Username =
    tblAssetUserRelations.Username
  Inner Join tblAssets On tblAssets.AssetID = tblAssetUserRelations.AssetID
  Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Where tblO365Group.DisplayName = '<YOUR O365 GROUP NAME>' And
  tblAssetUserRelations.Type = 1
NOTE: tblAssetUserRelations.Type = 1 by default is "Owned By".  If you don't have relationships setup you can leave this out.