Yep. The "i" in "risen" is pronounced with the same vowel from "bit", "it", "sit", "fit", "hit", "miss", "pick", "since" etc.

The "ea" in "reason" is pronounced with the same vowel from "beach", "cheat", "eat", "cheese", "beat", "feet", "heat", "free", "leap", "me", "need", "pee", "read", "see", "tea", "we" etc.

Yes, there is. In "reason", the "i" sound is longer, which is marked by the colon in the phonetic description /'riːzn/, whereas in "risen", you pronounce the "i" sound for a very short time in comparison: /ˈrɪzn/

... or another example :  'his' and 'he's'.

Risen has a short sound like 'his'.

Reason has a long sound like 'he's'.

Can you hear the difference between 'fizz' and 'fees'? The first is short and the second is long.

Well, the 'ris' part of 'risen' is the same as 'fizz' (short).

And the 'reas' part of 'reason' is the same as 'fees' (long).