Just by moving your variable declarations into the loop, your code works like you’d want it to. You want get a new random number every game – and each game is one iteration of your while (gamerunning == false) loop.
private static void Main(string[] args)
{
Random rnd = new Random();
bool gamerunning = false;
while (gamerunning == false)
{
int roll1 = rnd.Next(1, 7);
int roll2 = rnd.Next(1, 7);
int roll3 = rnd.Next(1, 7);
int roll4 = rnd.Next(1, 7);
int roll5 = rnd.Next(1, 7);
int roll6 = rnd.Next(1, 7);
int roll7 = rnd.Next(1, 7);
int roll8 = rnd.Next(1, 7);
int roll9 = rnd.Next(1, 7);
int roll10 = rnd.Next(1, 7);
int roll11 = rnd.Next(1, 7);
int roll12 = rnd.Next(1, 7);
int Player1Total = roll1 + roll2 + roll3;
int Player2Total = roll4 + roll5 + roll6;
int Player1Total2roll = roll7 + roll8;
int Player2Total2roll = roll9 + roll10;
int P1froll = roll11;
int P2froll = roll12;
int overallP1 = Player1Total + Player1Total2roll + P1froll;
int overallP2 = Player2Total + Player2Total2roll + P2froll;
int Player1Score = 0;
int Player2Score = 0;
Console.WriteLine("Press anything to roll your die");
Console.ReadKey();
Console.Clear();
Console.WriteLine("\nPlayer1 first dice is ", roll1);
Console.WriteLine("Player1 second dice is " + roll2);
Console.WriteLine("Player1 third dice is " + roll3);
Console.WriteLine("Your total is " + Player1Total);
Console.WriteLine("\nYour opponents first dice roll is " + roll4);
Console.WriteLine("Your opponents second dice roll is " + roll5);
Console.WriteLine("Your opponents third dice roll is " + roll6);
Console.WriteLine("Your opponents total is " + Player2Total);
Console.WriteLine("\nPlayer1 first dice is " + roll7);
Console.WriteLine("Player1 second dice is " + roll8);
Console.WriteLine("Your total is " + Player1Total2roll);
Console.WriteLine("\nYour opponents first dice roll is " + roll9);
Console.WriteLine("Your opponents second dice roll is " + roll10);
Console.WriteLine("Your total is " + Player2Total2roll);
Console.WriteLine("\nPlayer1 final roll is " + roll11);
Console.WriteLine("Your total is " + P1froll);
Console.WriteLine("\nYour opponents final roll is " + roll12);
Console.WriteLine("Your total is " + P2froll);
if (overallP1 > overallP2)
{
Player1Score++;
Console.WriteLine("\nPlayer 1 Wins");
Console.WriteLine("The Current Score is:");
Console.WriteLine("Player 1: " + Player1Score);
Console.WriteLine("Player 2: " + Player2Score);
}
else if (overallP2 > overallP1)
{
Player2Score++;
Console.WriteLine("\nPlayer 2 Wins");
Console.WriteLine("The Current Score is:");
Console.WriteLine("Player 1: " + Player1Score);
Console.WriteLine("Player 2: " + Player2Score);
}
if (overallP1 == overallP2)
Console.WriteLine("\nIt's a draw");
if (Player1Score >= 5)
gamerunning = true;
else if (Player2Score >= 5)
gamerunning = true;
//if ( Player1Score == Player2Score)
//{
// DiceRoll();
//}
}
}