FunctionsPublic/New-GraphFolderInRootGroup.ps1

function New-GraphFolderInRootGroup
{
    param([psobject]$accessToken, [string]$groupID, [string]$folderName)
    #
    # Create new unified group
    #
    $sendBody = @{
        "name" = "$($folderName)";
        "folder" = @{}
        } | ConvertTo-Json 
    $sendBody

    $responseBody = Invoke-RestMethod `
        -Uri "https://graph.microsoft.com/v1.0/groups/$($groupID)/drive/root/children" `
        -Headers @{"Authorization" = "Bearer $($accessToken.AccessTokenCredential.GetNetworkCredential().password)"} `
        -Body $sendBody `
        -ContentType "application/json" `
        -Method POST

    $jsonResponse = $responseBody | ConvertTo-JSON

    $createdFolder = ConvertFrom-Json -InputObject $jsonResponse

    return $createdFolder
}