As a service to my fellow forum members, i decided to collect some empirical data on talents to  help determine their level of randomness.
I decided to follow 
@CRABNUTZ 's advice and continue to roll until I received the 5/5 talent I was looking for (in this case 5/5 Missile Damage).
I repeated this experiment 5 times (feel free to PayPal me cash if you would like additional data sets).
It took me 299 rolls in total to obtain the five talents.  This is an average of 60 rolls per talent or 3,000 gold under the current 50 gold refresh price.   This is slightly less than 
@CRABNUTZ 's estimate of 3,500 gold.  I received the perfect talent in:
Try 1:  68 rolls
Try 2:  30 rolls
Try 3:  32 rolls
Try 4:  82 rolls
Try 5:  87 rolls
My theory before I started was that talents received earlier in a string of rolls were more likely to be lower level and as the rolls continued to be made, the chances of obtaining a perfect talents would increase.
For purposes of quantifying the data, I grouped rolls into sets of 10 (first ten rolls, then second ten, etc. ).  Here is the data I collected:
Rolls 1-10 (50 rolls)
1/5 Talent  30%
2/5 Talent  22%
3/5 Talent  24%
4/5 Talent  20%
5/5 Talent    4%
Rolls 11-21 (50 rolls)
1/5 Talent  24%
2/5 Talent  16%
3/5 Talent  32%
4/5 Talent  22%
5/5 Talent    6%
Rolls 21-30 (50 rolls)
1/5 Talent  28%
2/5 Talent  28%
3/5 Talent  14%
4/5 Talent  20%
5/5 Talent  10%
Rolls 31-40 (32 rolls)
1/5 Talent  25%
2/5 Talent  22%
3/5 Talent  28%
4/5 Talent 12.5%
5/5 Talent 12.5%
Rolls 41-50 (30 rolls)
1/5 Talent  7%
2/5 Talent  27%
3/5 Talent  33%
4/5 Talent  23%
5/5 Talent  10%
Rolls 51-60 (30 rolls)
1/5 Talent  27%
2/5 Talent  37%
3/5 Talent  17%
4/5 Talent  10%
5/5 Talent  10%
Rolls 61-70 (20 rolls) 
1/5 Talent  11%
2/5 Talent  18%
3/5 Talent  14%
4/5 Talent  46%
5/5 Talent  11%
Rolls 71-80 (20 rolls)
1/5 Talent  25%
2/5 Talent    5%
3/5 Talent  20%
4/5 Talent  20%
5/5 Talent   30%
Rolls 81-90 (9 rolls)
1/5 Talent   0%
2/5 Talent  11%
3/5 Talent  22%
4/5 Talent   0%
5/5 Talent   66%
Even though the above data is from a lot of rolls, the sample size is still rather small to draw foregone conclusions.   Also, the fact that I stopped gathering data once I hit a specific 5/5 Talent skews the data as well.  And, the sample sizes for the latter groups of 10 are small and a couple of different results would paint a different picture.
Now, with those disclosures out of the way, as I look at the data, there certainly seems to be an increased likelihood of higher level talents as you progress through the rolls with a significant shift around the 60 roll mark.
The actual talents offered appear to be fairly random (i.e  RPG Health, Firebomb damage, etc.).
That being said, the other two premium talents that I would want (Flash and Firebomb Damage) were received only once each during these rolls. I received 5/5 Flash on Try 2 on my 80th roll (#82 was 5/5 Missile).  I received 5/5 Firebomb on Try 5 on my 56th roll (#87 was 5/5 Missile).
I hope this helps.   If i make another talent run I might update my results.