A cutting mat is essential.  It protects your table top from your rotary cutter (and also from the latex cleaner and glue) and prolongs the life of the blade of the rotary cutter (which are not cheap).

A white gel pen is essential for drawing pattern pieces onto the latex.  The ink can be removed with latex cleaner.   However it is always best to mark the reverse (matt) side of the latex just in case.  White is the best colour for most colours of latex, but for white latex you may prefer to get coloured pens – though I have found that these don’t clean off as well as the ink from white pens.

You will generally use the rotary cutter freehand.  However sometimes you will want to cut very straight lines (e.g. for contrast trims).  Using a rotary cutter with a normal ruler is not advisable.  The cutter can roll up onto the ruler damaging the straight edge of the ruler, blunting the cutter and potentially cutting your fingers.  A ruler that is designed for use with a rotary cutter has a vertical metal edge along which the side of the rotary cutter blade can run.
Jakar 60cm Acrylic Rule/Ruler with Steel Cutting Edge (Amazon)
Linex Hobby Cutting Ruler Anti-slip Light Aluminium 50cm (Amazon)

Glue spreaders

Seam roller

The roller is essential for creating strong seams.  All seams should be firmly rolled once you are happy with them. I bought a very cheap one from Wilkinson – which is fine. Any with a plastic roller would be okay (avoid those with a brass roller).
Harris Premier wallpaper edge seam roller (Amazon)

Masking tape

Masking tape is very useful to prevent latex from stretching, for example when cutting very thin strips, or when gluing areas that must be perfectly flat such as zips.
Tesa Sensitive Surfaces Low Tack Masking Tape With 7 Days Residue Free Removal, 30 mm x 50 m (Amazon)
Tesa Sensitive Surfaces Low Tack Masking Tape With 7 Days Residue Free Removal, 50 mm x 50 m (Amazon)

Scalpel handle and 10/10A blades

Having said above that a scalpel is useless, it is actually sometimes essential for very tiny cuts. A retractable blade handle is useful. The blades can be bought in 100s very cheaply.
’10A’ blades are pointed.
’10’ blades have a curved tip and are more suited to cutting latex.
Swann-Morton Retractaway Premium Knife + 5 10A blades (Amazon)
Swann-Morton Retractaway Knife Handle – just the handle (Amazon)
Swann-Morton non sterile blade No. 10A – pack of 100 (Amazon)
Swann Morton Non-Sterile Surgical Blade Remover Unit (Amazon)

Tweezers

A good pair of tweezers is essential. Undoing seems requires a firm but fine grip.
Tweezerman Green Tea Mini Slant Tweezer (Amazon)

Cling film

A roll of cling film can be cut (carefully, with a scalpel) into cling film tape of various widths.  This can then be used to protect cleaned and glued seams until ready for construction.

J Cloths

J cloths, cut into small pieces (e.g. 8x4cm) are ideal when using the thinner/cleaner to clean seams.  They are cheap enough that they can be disposed of as soon as they become ineffective.
Wilco’s ‘All purpose’ cloths (Wilco’s)

Scissors

A good quality pair of scissors is useful. Most scissors are hopeless are cutting latex.  These work really well:
CK Trimming Scissors 175mm / 7″ (Tooled Up)

Lining paper

Patterns can be drawn or printed onto lining paper and then cut out.  This paper is stiff enough that you can trace around it with the gel pen.
Wilco’s Lining Paper 1000g (Wilco’s)

Flexible ruler

A flexible ruler can be useful when drawing patterns by hand.
Prym 50cm Flexible Curved Rule (Amazon)

Pattern Tracing Wheel

A pattern tracing wheel can be used for transposing a commercial pattern pieces (provided on very flimsy tracing paper) onto lining paper more suited to use with latex.
Get Precise Pointed, High Grade Steel Needle-Pointed Tracing Wheel- Pattern Making, Pattern Tracing (Amazon)