When you use the help you can rely on the lowest note, but in the normal exercise you don't have the bass for reference, and the chords can be inverted. Listen instead to the quality of each chord, if it is major, minor, diminished... and the feeling of it, such as how it resolves when it is the root chord.

It is very hard without the bass, but it gets better with time. The first time you click to hear the chord progression you can hear a reference from the scale before the actual progression, you can use that to have the reference of the sound of the scale and where the root is.

And you can always use the warm up before going to the exercise, and put it as easy as you want to develop your ear from the ground level. Starting is the hardest part, and that exercise requires certain understanding of theory.

Good luck =)

Also, you can sing lines. So, if you hear DO - TI and MI - RE than it's I-V, but if you hear DO - TI and the MI stays the same, it's I-iii, for example. I actually force myself to do this, even when I already know the answer, so I can get the most benefit from the exercise. You can also sing the bass note that you think it might be to see if it works. Sing sing sing, my friend.