But that's the argument. Roma didn't have a world-class squad or coach back then, let alone comparable to ours. (Roma's squad wasn't even in the top three at the time – it was definitely us, Milan, and Juventus). Yes, in that season, they came very close to winning the title but didn't. But that's to be expected. In the long run, if you could somehow play that season over and over again with the same teams and coaches, Roma would win the league very few times, because Ranieri and Spalletti and most of their players simply weren't title-winning caliber. 2009–10 was odd in that Roma had a period of absolute awfulness under Spalletti and an amazing run of form under Ranieri, but in the end it evened out. Why did they keep getting whipped in CL? I suspect similar reasons – their squad simply wasn't good enough.
The hypothetical you're talking of – if Roma had world class squad and coach – is simply that, a hypothetical. Just about every circumstance you can think of when Roma choked is also a circumstance when Roma had less quality than their opponents. The two can't be separated.
I don't see the logic in saying that things like Arsenal or Wolfsburg are just normal occurrences/special circumstances for us but endemic of a pattern for Roma. Regardless of whether we were blown out or not, we were underachievers in Europe, and accusations of mentality issues weren't unheard of (even at Zanetti, no less). Did Roma falter in Europe more than we did? Probably, but that's par for the course. We had a better squad back than Roma, so of course we would lose less.