俩 is a fusion of 两 + 个, so the measure word is already baked in — never write 俩个 or follow it with any other measure word. Typical pairings are with people pronouns: 我们俩, 你们俩, 他们俩.
mistakes
Don't confuse 俩 (liǎ, 'two of [people]') with 两 (liǎng, the standard number 'two' used before measure words). The same character 俩 is also read liǎng, but only as the bound morpheme in 伎俩 ('trick'). Outside that one compound, 俩 = liǎ.
Left-side person radical, the side-form of 人. This is the semantic anchor: the liǎ reading counts only people, never objects, and 亻 is what tells you so. For pairs of things use 两 + measure word instead.
Right side 两 supplies both sound (liǎng → liǎ) and meaning. Combined with the person radical, 两 fuses with an implicit measure word 个 — so 俩 already means 'two of them (people)' on its own; never write 俩个. The other reading liǎng survives only in 伎俩.
