public class Die
{
    private readonly Random _random;
    private readonly int _numberOfSides;

    public Die(int numberOfSides)
    {
        if(numberOfSides < 2)
            throw new ArgumentException(string.Format(GameComponentsResources.InvalidNumberOfSides, numberOfSides));

        _numberOfSides = numberOfSides;
        _random = new Random();
    }

    public int Roll()
    {
        return _random.Next(1, _numberOfSides);
    }
}

protected virtual long GetSeed() //could be a property too
{
    return Environment.TickCount; //or whatever
}