As the language of the Minoan Crete is irrevocably lost, the only clue to reconstruct bits of it, lies with the only written remnants of Crete's history from that age: the famous Linear A and Hieroglyphic documents (not counting the Phaistos disc). But with no one to tell us how to read those inscriptions, currently our only clue to the true phonetic values those signs hide, is some sort of 'back-tracing' of signs from the Linear B system.
I won't cover details of the Linear B writing system: one can find enough appropriate desription of the Linear B syllabary in any library or on the web. It is enough to say that the Linear B "alphabet" is one of the simpler writing systems of the ancient middle east: almost every (if not all) of its signs are of the structure CV or V (C=consonant, V=Vowel). This syllabary encompasses roughly about 100 signs (including those with an unidentified value). In addition to the syllabary, various ideograms are also used on the tablets as tools of a scribal stenography.
If one looks at the Linear A signs, similarities with the (younger) Linear B alphabet become too obvious to be ignored. Many of the signs can be identified one-to-one without doubt. But there are a handful of them, that do not display such counterparts. At least not one to be identified at first sight. But some of them have gradually found their counterpart thanks to the relentless work of scholars. Currently, there are so many identified linear A and B sign-pairs, that we may assume: almost all Linear B signs must have a Linear A ancestor, and most Linear A signs were continued to see use in the (Greek) Linear B inscriptions.
So, if we have a one-to-one relationship regarding most of these signs, then why not go and find the missing pairs? This is exactly what I tried with the following Linear B signs: LinB *72 (PE) and LinB *68 (RO2). Up to date, there have been but little suggestions on whether these signs had any Linear A counterpart.
As for the sign LinB *72, the sign displays a characteristic 'humpy' shape to the side, with a horizontal symmetry axis, consisting only of straight lines (check it here).
Now, in linear A we had a sign, labelled LinA *305, that has a fairly similar layout: Consising of straight lines only, having a horizontal axis of symmetry, with a fair degree of resemblance to the greek letter capital sigma ('summa sign'). (If you want, you can check its details here)
Now what if this identification is correct, and the sign LinA *305 is indeed the same as LinB *72? It is obvious that LinA *305 is primarily not an ideogram, it is too frequently used as a component of words. We can directly check it in the Linear A texts (thanks to John Younger for that). On the HT9 tablet,line b2, we see KA-*305, a term contrasted to the term SA-*315 in the first line, on the other side. Since we may observe a term KA-PA as a very common transaction term on the Haghia Triada tablets, it is more than tempting to assume a reading KA-PE for HT9b.2. As for the other occurrances of *305 as a phonetic sign, HT10a3-4 gives the reading PE-RU, HT27a.4-5 KU-PE (this may be connected to KU-PA, another word appearing on the tablets - e.g. on ZA11), HT146.3 RI-PE, Kh7a.4 SE-PE, PE2.2 RU-PIPE-MI, PHZb48 QA-PE, ZA6a.1 PE-WA-NA, etc.
The same method can be applied to the Linear B sign *68 (RO2). It is a 'lyre-like' sign, with vertical symmetry axis, and has an inner cross that is already pretty much like the bare RO sign LinAB *02. I would propose an identity of the LinA *68 with the LinA *315 sign. The latter has similarity to LinAB *02 as well, though it is not always perfectly symmetric with a vertical axis. Again, LinA *315 is more of a phonetic sign than a logogram. Now, if we use this value to read Linear A texts, we may get some interesting results (the truth is, that the identification of these occurrences of LinA *315 with the phonetic value RO has already been proposed by John Younger). But let us not simply subsitute RO to these places but RO2 (which might have been *RYO). This way, we see the word SA-RO2 on the mentioned HT9 tablet. This reading does not seem imaginary, since we have a very common transaction term on the tablets: SA-RA2. Another nice thing is to observe, is that SA-RA2 never alternates with *SA-RA. This reminds us that the reading of RA2 was different from that of RA (it is often assumed to be RYA). But the term KU-RO can alternate with the term KU-RA (e.g. ZA20). In turn SA-RA2 seems to alternate with SA-RO2.