QFontDatabase::addApplicationFont Linux not working

[Erakis]

Hi, I'm trying to use a custom font in a Qt Quick application.

1 - First of all I add the "Roboto-Regular.ttf" to my resource file.

<RCC>
    <qresource prefix="/">
        <file>main.qml</file>
         .....
        <file>Fonts/Roboto-Regular.ttf</file>
    </qresource>
</RCC>

2 - I load the font and set up as default for the application. I can see the "Roboto" file display in the database while enumerating the font family

    QFontDatabase::addApplicationFont(":/Fonts/Roboto-Regular.ttf");
    QFontDatabase database;
    foreach (const QString &family, database.families()) {
        qDebug() << family;
    }
    QFont font("Roboto");
    app.setFont(font);

3 - On the QML side, I have :

Text { 
      Text : "\u2794"
}

4 - On Windows 7 and Linux Ubuntu this is well working, I'm seeing the symbol char
5 - I try it on a Linux (custum image build with Yocto) but I got an empty text. No symbol displayed :( What could be the problem ? I try setting manually the font to the text item

Text { 
      font.family : "Roboto"                // Not work
      font.family : "Roboto-Regular"        // Not work
      Text : "\u2794"
}

I'm really out of idea.