Yes—HP5+ is very tolerant of exposure and development variation, so rolls shot at EI 200 and EI 400 can usually be developed together with little trouble. A practical baseline from Ilford’s recommendations is about 11 minutes in Rodinal 1:50 at 20°C for HP5+ exposed at 400. If one roll was exposed at 200, developing both for around 12 minutes is likely to give acceptable results.

The safest approach is to trust the manufacturer’s data sheet first, especially when online charts disagree. Massive Dev Chart can be useful, but it is user-contributed and not always as reliable as Ilford’s published data.

A few notes:

• Expect noticeable grain with HP5+ in Rodinal; many photographers like this look.
• Small time differences like 11 vs 12 minutes are not critical with HP5+.
• If consistency matters, test a roll and adjust for your agitation, thermometer accuracy, and scanning/printing preferences.

Some photographers also use highly dilute Rodinal stand development for a different look, but that’s more experimental and not the best starting point if you want predictable results.