Assuming you have a random room number generated, you can make the string like this :
char buffer[16];
sprintf( buffer, "host%d", roomNumber );
To generate the random room number I would use this :
int GetRandomValue( int minval, int maxval )
{
int span = maxval - minval;
int rval = rand() % span;
int result = rval + minval;
return result;
}
If you want rooms to range from 101 to 110 then pass those two values to the function :
int room = GetRandomValue( 101, 110 );