JOINT FILING AGREEMENT
EXHIBIT A
The undersigned each agree that (i) the statement on Schedule 13D relating to the common units
representing limited partnership interests of Eagle Rock Energy Partners, L.P., a Delaware limited
partnership, has been adopted and filed on behalf of each of them, (ii) all future amendments to
such statement on Schedule 13D will, unless written notice to the contrary is delivered as
described below, be jointly filed on behalf of each of them, and (iii) the provisions of Rule
13d-1(k)(1) under the Securities Exchange Act of 1934 apply to each of them. This agreement may be
terminated with respect to the obligation to jointly file future amendments to such statement on
Schedule 13D as to any of the undersigned upon such person giving written notice thereof to each of
the other persons signatory hereto, at the principal office thereof.
| Dated: November 13, 2006 | EAGLE ROCK HOLDINGS, L.P. By its general partner Eagle Rock GP, L.L.C. |
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| By: | /s/ Xxxxxxx X. Xxxxx | |||
| Xxxxxxx X. Xxxxx | ||||
| Manager | ||||
| Dated: November 13, 2006 | EAGLE ROCK GP, L.L.C. |
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| By: | /s/ Xxxxxxx X. Xxxxx | |||
| Xxxxxxx X. Xxxxx | ||||
| Manager | ||||
| Dated: November 13, 2006 | NATURAL GAS PARTNERS VII, L.P. |
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| By: | /s/ Xxxxxxx X. Xxxxx | |||
| Xxxxxxx X. Xxxxx | ||||
| Authorized Member | ||||
| Dated: November 13, 2006 | NATURAL GAS PARTNERS VIII, L.P. |
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| By: | /s/ Xxxxxxx X. Xxxxx | |||
| Xxxxxxx X. Xxxxx | ||||
| Authorized Member | ||||
| Dated: November 13, 2006 | By: | /s/ Xxxxxxx X. Xxxxx | ||
| Xxxxxxx X. Xxxxx | ||||
