You didn’t say what you want to do with the bit that drops off the end.
Assuming you want what PBP shift would do with a byte, and just drop the end bit,
and feed in a zero to the right.
Code:
dis var byte [4]

BitwiseRotateLeft:						' bitwise rotate array
  @ rlf 	_dis+3		,F				; ditching the first bit
  @ rlf		_dis+2		,F				;
  @ rlf		_dis+1		,F				;
  @ rlf		_dis+0		,F				;
  @ bcf		_dis+3		,0				;clear MSB
return
So long as you can access the first byte by aliasing it, I’m sure the assembler is a continuous 4 bytes.