Through Hrothgar's achievements the poet suggest his own system of values. What seems to matter most to the people in his society?

The poet doesn't spend a lot of time in
Beowulf extolling the virtues of Hrothgar.  For most of the story,
Hrothgar is therather defeated king of a people plagued by a ravaging monster.  In the
geneology at the beginning of the work which explains how Hrothgar assumed the throne,
we do see what Hrothgar once was--and will presumably become again once Grendel and his
mother are dead. 

The text I'm using is the Seamus Heaney
translation, but the ideas will be similar in all translations, I presume.  There
are three aspects of life which seem to matter most to the people of the day, as valued
by the poet(s) who sang/wrote Beowulf.  (This corporate authorship
over time adds a complication to your question, which refers to a single poet.  The
values of every poet who passed on the story as well as the monks who finally
transcribed it from an oral story into a written one--as well as the translators, to
some degree--are undoubtedly reflected in the finished work, as well. However, we have
to deal with one text, so here goes.) We'll presume the poet/storyteller sang/spoke
about what mattered to the people for whom he
performed.

The first thing we learn is that Hrothgar was an
effective leader.  We read that "the fortunes of war favored Hrothgar."  He was
apparently an effective leader in battle. 

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Friends and kinsmen flocked to his
ranks,

young followers, a force that
grew

to be a mighty
army.

This is evidence that a
good leader is one who can win in battle--something which was quite common in that place
and time.  People were willing to follow someone who could defeat his enemies. 
Ironically, of course, Hrothgar will later be paralyzed, in a way, by the marauding
Grendel.  But not so in the beginning.

The next thing
Hrothgar did which shows us what the poet, and presumably the people, valued was to
build a great hall. 

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                           ...So his mind
turned

to hall-building: he handed down
orders

for men to work on a great
mead-hall

meant to be a wonder of the world
forever.

This great hall
served the dual purpose of protection from enemies, as it's the place all would come for
shelter from whatever danger was upon them, and a symbol of a town's greatness to the
rest of the world.  Remember, their world was a much smaller place than anything we
might mean by "the world."  It was a sign of greatness and power to have a fine, artful,
and grand hall in a town.  It's the first thing Hrothgar did after returning from his
successes in battle, indicating the great value of a great hall.  Again, ironically,
this hall is virtually emptied by the threatening presence of
Grendel.

Finally, Hrothgar was faithful to reward those who
deserved it. He "doled out rings/ and torques at the table."  This is a picture of a
gracious and grateful king.  Being recognized and rewarded for services rendered was a
value of the poets, and presumably all Anglo-Saxons.  This giving of gifts as a reward
for services rendered is a foreshadowing of what's to come for
Beowulf.