It depends what technologies you're interested in. If you're excited about big stone buildings, then the post-Roman early middle ages are a dark time. If, however, you're interested in the sorts of technologies that farmers care about -- knives, ploughs, etc -- the picture is different. The key to this all, I personally think, comes down to economic infrastructure.

The Roman economy excelled at concentrating surplus. They never really transformed the Mediterranean into an integrated economic zone, but they did manage to take the extra resources from all the different regions around the Mediterranean and pool them into massive cities like Rome, Carthage, and later Constantinople and Ravena. There, in these cities, they undertook massive building projects that were only possible thanks to the huge concentrations of wealth and people that their redistributive taxation practices created. Massive bathhouses, water works, 7 story tall apartment buildings, art made from stone tiles taken from all around the periphery of the Mediterranean: this was all possible not so much because of Roman engineering brilliance, but because they had the resources to centralize enough stuff to finance it all.

In the post-Roman 'dark ages,' no one in the west had the finances to do anything comparable. Even in the east, the Byzantine Empire struggled to maintain a sufficient taxation base (especially after the plagues of the sixth century and the conquest / defection of their most profitable provinces to the new Islamic empire. But in the west, many regions' economies collapsed down to small rural farmsteads with little to no ability to pool surplus at all. These small farms had to build new local economies, in some cases, from the ground up.

There was a lot of technological innovation in these communities, but much of it was at a lower level of complexity than what we'd seen in the Roman empire. The Romans ate off fine pottery manufactured in N. Africa in huge workshops which existed thanks to the shipping routes that were created by the grain taxation demands of the city of Rome. That is, this industry grew highly specialized because the Roman redistributive economy of Roman imperialism. When those grain shipments ended, the pottery industry began a slow death. Meanwhile, in rural Britain, the fine Roman wears disappeared entirely, and were replaced with horrible quality local handbuilt pottery -- the kinds of pots you make from mud in your back garden, a decided inferior product. Yet remember that we are comparing industrial products that existed because of imperial resource pooling with locally manufactured pots -- this isn't so much a change in technology as it is a loss of economic centralization and specialization.

As time passed, the products of these local rural communities slowly began to improve as their makers gained in skill and specialization. By the sixth century, rural itinerant blacksmiths in England were making better knife blades that had been made in the height of Roman quasi-industrial production. By the seventh century, some of these smiths had established permanent workshops where they were making knives almost as good as our own. Plough technology improved immensely in efficiency in the seventh century. The pottery industry recovered and began producing wheel-thrown pottery again.

So rather than viewing the Roman empire's fall in the west and contraction in the east as a setback for technological advancement, I would suggest framing it instead in terms of how individual technological experts respond to changing resources. The economic conditions under which craftspersons worked in western Europe in the sixth century were vastly more limited than those enjoyed by craftspersons living near imperial centers in the second, but these persons nevertheless managed to improve the technologies they were able to produce with the resources they had. These resources were, however, much more limited by locality, and large, showy Roman building projects were replaced with the smaller, yet no less innovative and creative, advancements in things like the metallurgy of portable iron tools.