Curled tomato leaves are not always an insect. Check the newest growth first: if the shoot tip is curled and distorted, something may be feeding there. If the lower leaves have rolled upward and feel firm and leathery, it is usually physiological leaf roll, linked to hot, dry weather, rapid growth or pruning, and no pest control will change it. Narrow, twisted new growth points to herbicide instead.
The rest of what gets called “curling leaves on tomato plants”. Some are pests we have not profiled yet; some are insects doing you a favour; some are not insects at all, and no treatment will help.
Leaf margins rolled upward until they touch or overlap, firm and leathery to the touch, lower leaves first. It follows hot, dry weather, rapid growth or pruning, does not noticeably reduce growth or yield, and needs no treatment.
New leaves narrow, elongated or twisted and cupped, with parallel veins, failing to expand. Causes include spray drift, a sprayer previously used for weedkiller, and mulch of treated lawn clippings; manure, compost, hay or straw carrying aminopyralid, clopyralid or picloram residues does the same.
Small leaves that curl upward and crumple, with yellow margins and between the veins, on a stunted, upright, bushy plant. Spread by the tobacco whitefly, so look for the insect to confirm it.
Silverleaf whitefly →Four questions about the damage separate these better than an appearance can, and this page answers some of them for you.