What is the relation between a helicopter's length and rotor diameter?
Important.  I am a helicopter pilot, with no expertise or experience in design so I can give you reasons for this, but not design detail.

Most design decisions are compromises.  Helicopter rotors are definitely compromises.

What is the aim of the rotor design?
To have the smallest possible rotor to achieve the performance requirements of the craft.

What limits the smallest size?
Let's assume that the blades are as efficient at generating lift as you can make them.  There are only 2 ways to increase lift for any given blade at any given angle of attack.  That is to increase the length of the blade or to move it faster through the air, i.e. to make the rotor spin faster.

What limits the speed at which the rotor can rotate?
As the blade tip speed gets faster, drag increases with the square of the speed.  Increased drag means increased power required which means heavier engine and heavier gearbox.  As speed moves to a high percentage of supersonic, turbulence and therefore drag increases enormously.  The longer the blade, the lower the possible rotor RPM since the tip approaches supersonic speed more quickly.

Why not just increase the length?
Because the blade becomes increasingly difficult (and expensive) to manufacture to handle the loads on the blade and the heavier they become requiring more robust and heavier rotors hub assemblies.  

The inner part of the rotor also produces little lift since it is moving relatively slowly and since lift decreases with the square of the speed, the lift generated falls away rapidly as you move to the inside portion of the disc.  As you increase the length of the blade, without being able to increase the speed of the disc as above, the area of the disc which is "useless", increases as a proportion of the overall disc size.  Therefore, more power is needed to rotate the increasingly large useless area of the disc.

The lower the disc loading, the more efficient the helicopter is in the hover.
The disc loading is the ratio of the weight of the helicopter and the area the rotor disc describes as it rotates.  The disc loading should be as low as possible to reduce the required strength, and thus weight, of the blades especially as the weight of the helicopter increases under positive G which in turn increases the disc loading.

Non-performance considerations.  Parking; hangar space required; ability to operate in confined areas. 

Given these (and other design parameters), the rotor sizes you quote will have been arrived at by factoring each of the variables to find the best compromise, according to the designer, between them to achieve the desired performance goals.

Therefore, I don't believe that there is a relationship between the fuselage length and rotor size, possibly with some influence from the need to park and hangar the resulting craft.

[EDIT]
I've been hoping that some better informed answers would be added.  As there are none, I'll continue with my simple pilot guesswork.

What is the aim of the fuselage design?
To have the smallest possible fuselage to achieve the performance requirements of the craft.

What limits the smallest size?
How many crew?  How many PAX?  Level of comfort (utilitarian - R22, or comfortable - Long Ranger).  Fuel load.  Engine and gearbox size.  Cargo and other payload.  Baggage stowage?

What limits the maximum size?
Weight.  Profile drag.  Cost to manufacture.

Non-performance considerations.  Parking; hangar space required.