How do I implement a rotate left 1 bit operation in a 16-bit ALU in logisim
The simplest thing is to just add the input number to itself. Doubling a number (multiplication by 2) is equivalent to a left shift in binary. In other words, select ADD as the ALU operation, and feed the input value to both inputs of the ALU. If you do add-with-carry, then the carry bit will automatically get shifted into the LSB. In either case, the carry-out will be the MSB of the original input number.